Compilare: main.cpp: In function 'int main()': main.cpp:24:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size();++i) ~^~~~~~~~~ main.cpp:32:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<f[i].size();++j) ~^~~~~~~~~~~~ main.cpp:35:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(st[pi]!=-1&&dr[pi]!=a.size()) main.cpp:48:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i!=a.size()) ~^~~~~~~~~~ main.cpp:10:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.in","r",stdin); ^ main.cpp:11:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("charlie.out","w",stdout); ^