diff --git a/others/kirill`s/lab1/compile.sh b/others/kirill`s/lab1/compile.sh
deleted file mode 100755
index f71c378..0000000
--- a/others/kirill`s/lab1/compile.sh
+++ /dev/null
@@ -1 +0,0 @@
-g++ task18.cpp -o task18
diff --git a/others/kirill`s/lab1/file.in b/others/kirill`s/lab1/file.in
deleted file mode 100644
index 67420cc..0000000
--- a/others/kirill`s/lab1/file.in
+++ /dev/null
@@ -1,11 +0,0 @@
-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/in.txt b/others/kirill`s/lab1/in.txt
new file mode 100644
index 0000000..f2b6b71
--- /dev/null
+++ b/others/kirill`s/lab1/in.txt
@@ -0,0 +1,2 @@
+123456
+123456
\ No newline at end of file
diff --git a/others/kirill`s/lab1/task18.cpp b/others/kirill`s/lab1/task18.cpp
index 9b71547..13839d7 100644
--- a/others/kirill`s/lab1/task18.cpp
+++ b/others/kirill`s/lab1/task18.cpp
@@ -1,96 +1,123 @@
-#include <iostream>
-#include <fstream>
-#include <string>
+#include <unistd.h>
 #include <sys/stat.h>
-#include <cstdlib>
-#include <cerrno>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
 
-static bool file_exists(const std::string &path) {
-    struct stat st{};
-    return ::stat(path.c_str(), &st) == 0;
+#define RBUFSZ 4096
+#define WBUFSZ 4096
+
+static void die_perror(const char *what, const char *path, int exit_code) {
+    int saved = errno;
+    char msg[512];
+    if (path) {
+        snprintf(msg, sizeof(msg), "%s: %s: %s\n", what, path, strerror(saved));
+    } else {
+        snprintf(msg, sizeof(msg), "%s: %s\n", what, strerror(saved));
+    }
+    (void) write(STDERR_FILENO, msg, strlen(msg));
+    _exit(exit_code);
 }
 
-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";
-}
-
-static bool parse_nonneg_ll(const char *s, long long &out) {
-    if (!s || *s == '\0') return false;
-    char *end = nullptr;
+static long long parse_ll(const char *s) {
+    char *end = NULL;
     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;
+    long long v = strtoll(s, &end, 10);
+    if (errno != 0 || end == s || *end != '\0' || v < 0) {
+        errno = EINVAL;
+        return -1;
+    }
+    return v;
 }
 
 int main(int argc, char *argv[]) {
-    if (argc != 3) {
-        std::cerr << "Usage: " << argv[0] << " input_file replace_count\n";
+    if (argc != 4) {
+        const char *usage =
+                "Usage: lab1_var_thirds_line <input.txt> <output.txt> <max_replacements>\n"
+                "Replace every third byte in each line with a space; counter resets after each newline.\n";
+        (void) write(STDERR_FILENO, usage, strlen(usage));
         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;
-    }
+    const char *in_path = argv[1];
+    const char *out_path = argv[2];
+    long long cap = parse_ll(argv[3]);
+    if (cap < 0) die_perror("invalid max_replacements", argv[3], -1);
 
-    if (!file_exists(in_path)) {
-        std::cerr << "Error: input file does not exist.\n";
-        return -1;
-    }
+    int in_fd = open(in_path, O_RDONLY);
+    if (in_fd < 0) die_perror("open input failed", in_path, -1);
 
-    std::ifstream in(in_path);
-    if (!in) {
-        std::cerr << "Error: cannot open input file.\n";
-        return -1;
-    }
+    mode_t perms = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH; /* 0666 */
+    int out_fd = open(out_path, O_CREAT | O_WRONLY | O_TRUNC, perms);
+    if (out_fd < 0) die_perror("open output failed", out_path, -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;
-    }
+    char rbuf[RBUFSZ];
+    char wbuf[WBUFSZ];
+    size_t wlen = 0;
 
-    long long replacements = 0;
-    std::string line;
+    long long total = 0;
+    long long col = 0; /* position in current line starting from 1 */
+    int replacing_enabled = 1;
 
-    while (std::getline(in, line)) {
-        if (!line.empty() && replacements < target) {
-            for (std::size_t idx = 0; idx < line.size() && replacements < target; ++idx) {
-                std::size_t pos1 = idx + 1;
-                if ((pos1 % 3) == 0) {
-                    if (line[idx] != ' ') {
-                        line[idx] = ' ';
-                        ++replacements;
+    for (;;) {
+        ssize_t n = read(in_fd, rbuf, sizeof(rbuf));
+        if (n > 0) {
+            for (ssize_t i = 0; i < n; i++) {
+                unsigned char c = (unsigned char) rbuf[i];
+
+                if (c == '\n') {
+                    /* newline is written as-is and resets counter */
+                    if (wlen == sizeof(wbuf)) {
+                        ssize_t wrote = write(out_fd, wbuf, wlen);
+                        if (wrote < 0 || (size_t) wrote != wlen) die_perror("write failed", out_path, -1);
+                        wlen = 0;
+                    }
+                    wbuf[wlen++] = '\n';
+                    col = 0;
+                    continue;
+                }
+
+                col++; /* advance within the current line */
+
+                unsigned char outc = c;
+                if (replacing_enabled && (col % 3 == 0)) {
+                    if (total < cap) {
+                        outc = ' ';
+                        total++;
+                        if (total == cap) replacing_enabled = 0;
+                    } else {
+                        replacing_enabled = 0;
                     }
                 }
+
+                if (wlen == sizeof(wbuf)) {
+                    ssize_t wrote = write(out_fd, wbuf, wlen);
+                    if (wrote < 0 || (size_t) wrote != wlen) die_perror("write failed", out_path, -1);
+                    wlen = 0;
+                }
+                wbuf[wlen++] = (char) outc;
             }
-        }
-        out << line;
-        if (!in.eof()) out << '\n';
-        if (!out) {
-            std::cerr << "Error: write error.\n";
-            return -1;
+        } else if (n == 0) {
+            if (wlen > 0) {
+                ssize_t wrote = write(out_fd, wbuf, wlen);
+                if (wrote < 0 || (size_t) wrote != wlen) die_perror("write failed", out_path, -1);
+                wlen = 0;
+            }
+            break;
+        } else {
+            die_perror("read failed", in_path, -1);
         }
     }
 
-    if (!in.eof() && in.fail()) {
-        std::cerr << "Error: read error.\n";
-        return -1;
-    }
+    if (close(in_fd) < 0) die_perror("close input failed", in_path, -1);
+    if (close(out_fd) < 0) die_perror("close output failed", out_path, -1);
 
-    if (replacements != target) {
-        std::cerr << "Error: could not perform exactly requested replacements.\n";
-        return -1;
-    }
+    char res[64];
+    int m = snprintf(res, sizeof(res), "%lld\n", total);
+    if (m > 0) (void) write(STDOUT_FILENO, res, (size_t) m);
 
-    std::cout << replacements << std::endl;
-    return 0;
+    int exit_code = (int) (total & 0xFF);
+    return exit_code;
 }
diff --git a/others/vlad`s/lab1/in.txt b/others/vlad`s/lab1/in.txt
index 69e5568..50fee4e 100644
--- a/others/vlad`s/lab1/in.txt
+++ b/others/vlad`s/lab1/in.txt
@@ -1 +1,2 @@
-aaaaabababbabababaaabbbbabababbbaabbaabbabb
\ No newline at end of file
+aaaaaa
+aaaaaa
\ No newline at end of file