Compilare: user.cpp: In function ‘int main()’: user.cpp:86:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < ans.size (); ++ i) ^ user.cpp:90:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < ans.size (); ++ i) { ^ user.cpp:103:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < ans.size (); ++ i) { ^ user.cpp:50:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("johnie.in", "r", stdin); ^ user.cpp:51:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("johnie.out", "w", stdout); ^ user.cpp:53:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d", &n, &m); ^ user.cpp:56:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d", &x, &y); ^