Compilare: user.cpp: In function ‘int main()’: user.cpp:35:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<m[x].size();++i) { ^ user.cpp:46:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<m[curr].size();++j) { ^ user.cpp:11:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marmelada.in","r",stdin); ^ user.cpp:12:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marmelada.out","w",stdout); ^ user.cpp:14:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d",&N,&M,&S,&D); ^ 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); ^ user.cpp:21:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&c[i].first); ^