diff --git a/lab_1/12_first_symbols_to_spaces.cpp b/lab_1/12_first_symbols_to_spaces.cpp
index c8f2efb..825d0af 100644
--- a/lab_1/12_first_symbols_to_spaces.cpp
+++ b/lab_1/12_first_symbols_to_spaces.cpp
@@ -1,31 +1,50 @@
-// Task 12 (Ubuntu): replace every char equal to the first char of its line with a space.
-// Usage: ./task12 <input_file>  → writes "<input_file>.out" and prints replacement count.
-
 #include <iostream>
 #include <fstream>
 #include <string>
 #include <sys/stat.h>
+#include <cerrno>
+#include <cstdlib>
+#include <climits>
 
-// True if file exists (POSIX stat)
 static bool file_exists(const std::string &path) {
     struct stat st{};
-    return ::stat(path.c_str(), &st) == 0;
+    return ::stat(path.c_str(), &st) == 0; // stat success => exists [web:59]
 }
 
-// "<name>.out" by replacing last extension or appending if none
 static std::string make_out_name(const std::string &in) {
     std::size_t pos = in.find_last_of('.');
     if (pos == std::string::npos) return in + ".out";
     return in.substr(0, pos) + ".out";
 }
 
-int main(int argc, char *argv[]) {
-    if (argc != 2) {
-        std::cerr << "Usage: " << argv[0] << " <input_file>\n";
+static void print_usage(const char* prog) {
+    std::cerr << "Usage: " << prog << " <input_file> <replace_count>\n"; // positional args [web:59]
+}
+
+static bool parse_ll(const char* s, long long& out) {
+    if (!s || !*s) return false;
+    errno = 0;
+    char* end = nullptr;
+    long long v = std::strtoll(s, &end, 10); // use endptr and errno [web:59]
+    if (errno == ERANGE) return false;
+    if (end == s || *end != '\0') return false;
+    out = v;
+    return true;
+}
+
+int main(int argc, char* argv[]) {
+    if (argc != 3) {
+        print_usage(argv[0]);
         return -1;
     }
 
     std::string in_path = argv[1];
+    long long replace_limit = 0;
+    if (!parse_ll(argv[2], replace_limit) || replace_limit < 0) {
+        std::cerr << "Error: replace_count must be a non-negative integer.\n";
+        return -1;
+    }
+
     if (!file_exists(in_path)) {
         std::cerr << "Error: input file does not exist.\n";
         return -1;
@@ -44,18 +63,17 @@ int main(int argc, char *argv[]) {
         return -1;
     }
 
-    long long replacements = 0;
+    long long performed = 0;
     std::string line;
 
-    while (std::getline(in, line)) {
+    while (performed < replace_limit && std::getline(in, line)) { // stop early when limit hit [web:59]
         if (!line.empty()) {
             char first = line.front();
             for (char &c: line) {
-                if (c == first) {
-                    if (c != ' ') {
-                        c = ' ';
-                        ++replacements;
-                    } // count only real changes
+                if (c == first && c != ' ') {
+                    c = ' ';
+                    ++performed;
+                    if (performed >= replace_limit) break; // cap reached [web:44]
                 }
             }
         }
@@ -67,6 +85,23 @@ int main(int argc, char *argv[]) {
         }
     }
 
-    std::cout << replacements << std::endl;
-    return static_cast<int>(replacements);
+    // If limit reached mid-file, copy the rest unchanged
+    if (performed >= replace_limit) { // stream may be mid-line or between lines [web:59]
+        // Write remaining lines as-is
+        if (!in.eof()) {
+            // Flush any remaining part of current line already written; then dump rest
+            std::string rest;
+            while (std::getline(in, rest)) {
+                out << rest;
+                if (!in.eof()) out << '\n';
+                if (!out) {
+                    std::cerr << "Error: write error.\n";
+                    return -1;
+                }
+            }
+        }
+    }
+
+    std::cout << performed << std::endl; // print actual replacements up to limit [web:59]
+    return 0; // success [web:59]
 }
diff --git a/lab_1/README.md b/lab_1/README.md
deleted file mode 100644
index 3ce0d41..0000000
--- a/lab_1/README.md
+++ /dev/null
@@ -1,28 +0,0 @@
-## README.md
-### Кратко
-Работу выполнил студент группы АВТ-418 Куриленко Платон Семенович, вариант 12.
-
-Программа построчно заменяет все символы, равные первому символу строки, на пробел; пишет результат в файл с суффиксом .out и выводит число замен в stdout.
-
-### Сборка
-```bash
-./compile.sh
-```
-
-### Использование
-```bash
-./12_first_symbols_to_spaces <input_file>
-```
-Имя вывода: исходное имя с заменой последнего расширения на .out, либо добавлением .out (пример: a.txt → a.out; data → data.out).
-
-### Коды возврата
-- 0 при успехе; число замен также печатается в stdout.
-- -1 при ошибке: сообщение об ошибке выводится в stderr.
-
-### Быстрый тест
-```bash
-./run.sh
-```
-
-### Примечания
-- Замены считаются только при реальной замене; если первый символ — пробел, такие позиции не увеличивают счётчик.
diff --git a/lab_1/README.txt b/lab_1/README.txt
deleted file mode 100644
index 5d886ad..0000000
--- a/lab_1/README.txt
+++ /dev/null
@@ -1,25 +0,0 @@
-1. Кратко
-Работу выполнил студент группы АВТ-418 Куриленко Платон Семенович, вариант 12.
-Программа построчно заменяет все символы, равные первому символу строки, на пробел; пишет результат в файл с суффиксом .out и выводит число замен в stdout.
-
-
-2.Сборка
-./compile.sh
-
-
-3. Использование
-./12_first_symbols_to_spaces <input_file>
-Имя вывода: исходное имя с заменой последнего расширения на .out, либо добавлением .out (пример: a.txt → a.out; data → data.out).
-
-
-4. Коды возврата
-    0 при успехе; число замен также печатается в stdout.
-    -1 при ошибке: сообщение об ошибке выводится в stderr.
-
-
-5. Быстрый тест
-./run.sh
-
-
-6. Примечания
-Замены считаются только при реальной замене; если первый символ — пробел, такие позиции не увеличивают счётчик.
diff --git a/lab_1/run.sh b/lab_1/run.sh
index 8d3156f..82379d7 100755
--- a/lab_1/run.sh
+++ b/lab_1/run.sh
@@ -1 +1 @@
-./12_first_symbols_to_spaces file.in
+./12_first_symbols_to_spaces file.in 3
diff --git a/ilya`s/1/file.in b/others/ilya`s/1/file.in
similarity index 100%
rename from ilya`s/1/file.in
rename to others/ilya`s/1/file.in
diff --git a/ilya`s/1/file.out b/others/ilya`s/1/file.out
similarity index 100%
rename from ilya`s/1/file.out
rename to others/ilya`s/1/file.out
diff --git a/ilya`s/1/signs b/others/ilya`s/1/signs
similarity index 100%
rename from ilya`s/1/signs
rename to others/ilya`s/1/signs
diff --git a/ilya`s/1/signs.cpp b/others/ilya`s/1/signs.cpp
similarity index 100%
rename from ilya`s/1/signs.cpp
rename to others/ilya`s/1/signs.cpp
diff --git a/others/kirill`s/lab1/compile.sh b/others/kirill`s/lab1/compile.sh
new file mode 100755
index 0000000..f71c378
--- /dev/null
+++ b/others/kirill`s/lab1/compile.sh
@@ -0,0 +1 @@
+g++ task18.cpp -o task18
diff --git a/others/kirill`s/lab1/file.in b/others/kirill`s/lab1/file.in
new file mode 100644
index 0000000..67420cc
--- /dev/null
+++ b/others/kirill`s/lab1/file.in
@@ -0,0 +1,11 @@
+abcdef
+abcdefg
+abcdefghij
+abc def
+x
+12
+123
+   (three spaces)
+abc
+ab cs s dds
+\tabcde\tf
\ No newline at end of file
diff --git a/others/kirill`s/lab1/task18.cpp b/others/kirill`s/lab1/task18.cpp
new file mode 100644
index 0000000..e1a3eeb
--- /dev/null
+++ b/others/kirill`s/lab1/task18.cpp
@@ -0,0 +1,67 @@
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <sys/stat.h>
+
+static bool file_exists(const std::string &path) {
+    struct stat st{};
+    return ::stat(path.c_str(), &st) == 0;
+}
+
+static std::string make_out_name(const std::string &in) {
+    std::size_t pos = in.find_last_of('.');
+    if (pos == std::string::npos) return in + ".out";
+    return in.substr(0, pos) + ".out";
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        std::cerr << "Usage: " << argv[0] << " <input_file>\n";
+        return -1;
+    }
+
+    std::string in_path = argv[1];
+    if (!file_exists(in_path)) {
+        std::cerr << "Error: input file does not exist.\n";
+        return -1;
+    }
+
+    std::ifstream in(in_path);
+    if (!in) {
+        std::cerr << "Error: cannot open input file.\n";
+        return -1;
+    }
+
+    std::string out_path = make_out_name(in_path);
+    std::ofstream out(out_path);
+    if (!out) {
+        std::cerr << "Error: cannot create output file.\n";
+        return -1;
+    }
+
+    long long replacements = 0;
+    std::string line;
+
+    while (std::getline(in, line)) {
+        if (!line.empty()) {
+            for (std::size_t idx = 0; idx < line.size(); ++idx) {
+                std::size_t pos1 = idx + 1;
+                if (pos1 % 3 == 0) {
+                    if (line[idx] != ' ') {
+                        line[idx] = ' ';
+                        ++replacements;
+                    }
+                }
+            }
+        }
+        out << line;
+        if (!in.eof()) out << '\n';
+        if (!out) {
+            std::cerr << "Error: write error.\n";
+            return -1;
+        }
+    }
+
+    std::cout << replacements << std::endl;
+    return static_cast<int>(replacements);
+}
diff --git a/others/vlad`s/lab1/compile.sh b/others/vlad`s/lab1/compile.sh
new file mode 100755
index 0000000..9b9046f
--- /dev/null
+++ b/others/vlad`s/lab1/compile.sh
@@ -0,0 +1 @@
+g++ task11.cpp -o task11
diff --git a/others/vlad`s/lab1/file.in b/others/vlad`s/lab1/file.in
new file mode 100644
index 0000000..a3ea8a7
--- /dev/null
+++ b/others/vlad`s/lab1/file.in
@@ -0,0 +1,13 @@
+aabbcc
+bookkeeper
+Mississippi
+x
+aa
+aba
+aaa
+baaa
+aaab
+abba
+1222333
+    (four spaces)
+--====
diff --git a/others/vlad`s/lab1/task11.cpp b/others/vlad`s/lab1/task11.cpp
new file mode 100644
index 0000000..3076b2d
--- /dev/null
+++ b/others/vlad`s/lab1/task11.cpp
@@ -0,0 +1,71 @@
+// Task 11: In every pair of identical adjacent characters, replace the second with a space.
+// Usage: ./task11 <input_file> -> writes "<name>.out" and prints replacements count.
+
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <sys/stat.h>
+
+static bool file_exists(const std::string &path) {
+    struct stat st{};
+    return ::stat(path.c_str(), &st) == 0;
+}
+
+static std::string make_out_name(const std::string &in) {
+    std::size_t pos = in.find_last_of('.');
+    if (pos == std::string::npos) return in + ".out";
+    return in.substr(0, pos) + ".out";
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        std::cerr << "Usage: " << argv[0] << " <input_file>\n";
+        return -1;
+    }
+
+    std::string in_path = argv[1];
+    if (!file_exists(in_path)) {
+        std::cerr << "Error: input file does not exist.\n";
+        return -1;
+    }
+
+    std::ifstream in(in_path);
+    if (!in) {
+        std::cerr << "Error: cannot open input file.\n";
+        return -1;
+    }
+
+    std::string out_path = make_out_name(in_path);
+    std::ofstream out(out_path);
+    if (!out) {
+        std::cerr << "Error: cannot create output file.\n";
+        return -1;
+    }
+
+    long long replacements = 0;
+    std::string line;
+
+    while (std::getline(in, line)) {
+        if (!line.empty()) {
+            for (std::size_t i = 1; i < line.size(); ++i) {
+                if (line[i] == line[i - 1]) {
+                    if (line[i] != ' ') {
+                        line[i] = ' ';
+                        ++replacements;
+                    }
+                    // Move to next position; overlapping pairs like "aaa":
+                    // i at 2 will compare line[2] with line[1] (now space) → no double count.
+                }
+            }
+        }
+        out << line;
+        if (!in.eof()) out << '\n';
+        if (!out) {
+            std::cerr << "Error: write error.\n";
+            return -1;
+        }
+    }
+
+    std::cout << replacements << std::endl;
+    return static_cast<int>(replacements);
+}