Compilare: user.cpp: In function ‘int main()’: user.cpp:27:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<S[a].size();++i) ^ user.cpp:37:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<S[a].size();++i) ^ user.cpp:11:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.in","r",stdin); ^ user.cpp:12:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.out","w",stdout); ^ user.cpp:13:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d%d%d%d\n",&n,&m,&x,&y);m;--m) ^ user.cpp:16:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&X,&Y); ^