Compilare: user.cpp: In function ‘int main()’: user.cpp:48:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < v[i].size (); k++) { ^ user.cpp:16:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("dubi.in", "r", stdin); ^ user.cpp:17:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("dubi.out", "w", stdout); ^ user.cpp:24:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &N); ^