diff --git a/others/vlad`s/lab1/task11.cpp b/others/vlad`s/lab1/task11.cpp
index 3076b2d..b52a420 100644
--- a/others/vlad`s/lab1/task11.cpp
+++ b/others/vlad`s/lab1/task11.cpp
@@ -1,10 +1,9 @@
-// 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>
+#include <cerrno>
+#include <cstdlib>
 
 static bool file_exists(const std::string &path) {
     struct stat st{};
@@ -17,13 +16,30 @@ static std::string make_out_name(const std::string &in) {
     return in.substr(0, pos) + ".out";
 }
 
+static bool parse_nonneg_ll(const char *s, long long &out) {
+    if (!s || *s == '\0') return false;
+    char *end = nullptr;
+    errno = 0;
+    long long v = std::strtoll(s, &end, 10);
+    if (errno != 0 || end == s || *end != '\0') return false;
+    if (v < 0) return false;
+    out = v;
+    return true;
+}
+
 int main(int argc, char *argv[]) {
-    if (argc != 2) {
-        std::cerr << "Usage: " << argv[0] << " <input_file>\n";
+    if (argc != 3) {
+        std::cerr << "Usage: " << argv[0] << " input_file replace_count\n";
         return -1;
     }
 
     std::string in_path = argv[1];
+    long long target = 0;
+    if (!parse_nonneg_ll(argv[2], target)) {
+        std::cerr << "Usage: " << argv[0] << " input_file replace_count\n";
+        return -1;
+    }
+
     if (!file_exists(in_path)) {
         std::cerr << "Error: input file does not exist.\n";
         return -1;
@@ -46,15 +62,13 @@ int main(int argc, char *argv[]) {
     std::string line;
 
     while (std::getline(in, line)) {
-        if (!line.empty()) {
-            for (std::size_t i = 1; i < line.size(); ++i) {
+        if (!line.empty() && replacements < target) {
+            for (std::size_t i = 1; i < line.size() && replacements < target; ++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.
                 }
             }
         }
@@ -66,6 +80,16 @@ int main(int argc, char *argv[]) {
         }
     }
 
+    if (!in.eof() && in.fail()) {
+        std::cerr << "Error: read error.\n";
+        return -1;
+    }
+
+    if (replacements != target) {
+        std::cerr << "Error: could not perform exactly requested replacements.\n";
+        return -1;
+    }
+
     std::cout << replacements << std::endl;
-    return static_cast<int>(replacements);
+    return 0;
 }