Compilare: main.cpp: In function 'int main()': main.cpp:52:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<xs.size();++i) ~^~~~~~~~~~ main.cpp:44:33: 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); ^ main.cpp:45:35: 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); ^ main.cpp:46:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ main.cpp:49:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^