Compilare: user.cpp: In function ‘void prim()’: user.cpp:23:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<vec[1].size();i++) ^ user.cpp:38:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<vec[n1].size();i++) ^ user.cpp:41:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<vec[n2].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:63:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<ans.size();i++) printf("%d %d\n",ans[i].first,ans[i].second); ^ user.cpp:50:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.in","r",stdin); ^ user.cpp:51:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.out","w",stdout); ^ user.cpp:52:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); ^ user.cpp:56:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d",&x,&y,&z); ^