Compilare: user.cpp: In function ‘int main()’: user.cpp:25:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(INPUT_FILE, "r", stdin); ^ user.cpp:26:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(OUTPUT_FILE, "w", stdout); ^ user.cpp:29:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%u %u", &N, &M); ^ user.cpp:40:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%u %u", &x, &y); ^