Compilare: user.cpp: In function ‘int main()’: user.cpp:24:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(v = 0; v < a [j].size(); v ++) ^ user.cpp:27:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < a[0].size(); i ++) ^ user.cpp:8:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hamilton.in","r",stdin); ^ user.cpp:9:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hamilton.out","w",stdout); ^ user.cpp:11:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:13:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x, &y, &c); ^