Compilare: user.cpp: In function ‘int main()’: user.cpp:17:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("android.in" ,"r", stdin ); ^ user.cpp:18:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("android.out","w", stdout); ^ user.cpp:20:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &N, &M); ^ user.cpp:38:18: warning: ‘y2’ may be used uninitialized in this function [-Wmaybe-uninitialized] for (int y2 = y2; y2 < M; y2 ++) { ^