diff --git a/02/src/main.c b/02/src/main.c
index 70ba1e7..59e6ba1 100644
--- a/02/src/main.c
+++ b/02/src/main.c
@@ -1,12 +1,23 @@
 /**
- * Copyright [2023] Jiří Štefka <jiriks74>
+ * Copyright [2024] Jiří Štefka <jiriks74>
  * Project: AdventOfCode
  * @file main.c
  * @brief Main entry point
  * @author jiriks74
  */
 
+#define _GNU_SOURCE
+
+#include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+enum STATUS {
+  DECREASING,
+  INIT,
+  INCREASING,
+};
 
 /**
  * @brief Main entry point
@@ -20,6 +31,81 @@ int main(int argc, char *argv[])
     int main_test(int argc, char *argv[])
 #endif
 {
-  printf("Hello world!\n");
+  FILE *file;
+  if (argc > 1)
+    file = fopen(argv[1], "r");
+  else {
+    fprintf(stderr, "No file was given.\n");
+    return 1;
+  }
+if (file == NULL) {
+    fprintf(stderr, "Couldn't open file '%s'\n", argv[1]);
+    return 1;
+  }
+
+  char *buffer = NULL;
+  size_t bufferSize = 0;
+  int status = INIT;
+  uint safeCount = 0;
+  while (getline(&buffer, &bufferSize, file) != -1) {
+    char *token = strtok(buffer, " ");
+    int previousLevel = 0;
+
+    if (sscanf(token, "%d", &previousLevel) == EOF) {
+      fprintf(stderr, "Error: Wrong input file format!");
+      return 1;
+    }
+
+    token = strtok(NULL, " ");
+    int currentLevel = 0;
+    if (sscanf(token, "%d", &currentLevel) == EOF) {
+      fprintf(stderr, "Error: Wrong input file format!");
+      return 1;
+    }
+    if (currentLevel > previousLevel)
+      status = INCREASING;
+    else
+      status = DECREASING;
+
+    if (status == INCREASING) {
+      if (currentLevel - previousLevel < 1 | currentLevel - previousLevel > 3)
+        continue;
+    } else {
+      if (previousLevel - currentLevel < 1 | previousLevel - currentLevel > 3)
+        continue;
+    }
+
+    token = strtok(NULL, " ");
+
+    bool finished = true;
+    while (token != NULL) {
+      previousLevel = currentLevel;
+      if (sscanf(token, "%d", &currentLevel) == EOF) {
+        fprintf(stderr, "Error: Wrong input file format!");
+        return 1;
+      }
+      if (status == INCREASING) {
+        if (currentLevel - previousLevel < 1 |
+            currentLevel - previousLevel > 3) {
+          finished = false;
+          break;
+        }
+      } else {
+        if (previousLevel - currentLevel < 1 |
+            previousLevel - currentLevel > 3) {
+          finished = false;
+          break;
+        }
+      }
+      token = strtok(NULL, " ");
+    }
+    if (finished)
+      safeCount++;
+  }
+  free(buffer);
+  fclose(file);
+
+  printf("Safe count: %d\n", safeCount);
+
   return 0;
 }