Compilare: user.cpp: In function ‘int main()’: user.cpp:34:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size()-1;++i) ^ user.cpp:42:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size()-1;++i) ^ user.cpp:25:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmap.in","r",stdin); ^ user.cpp:26:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cmap.out","w",stdout); ^ user.cpp:27:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:30:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^