Compilare: user.cpp: In function ‘int main()’: user.cpp:76:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<c.size();++i) ^ user.cpp:80:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<c[i].size();++j) ^ user.cpp:61:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in","r",stdin); ^ user.cpp:62:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out","w",stdout); ^ user.cpp:64:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:70:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^