Compilare: user.cpp: In function ‘int main()’: user.cpp:28:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v[i].size() < m) continue ; ~~~~~~~~~~~~^~~ user.cpp:10:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("facebook.in", "r", stdin); ^ user.cpp:11:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("facebook.out", "w", stdout); ^ user.cpp:12:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:15:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^