Compilare: user.cpp: In function ‘int main()’: user.cpp:23:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0;j<g[i].size();j++) fr[v[g[i][j]]]=1; ^ user.cpp:14:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("3color.in","r",stdin); ^ user.cpp:15:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("3color.out","w",stdout); ^ user.cpp:16:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&n,&m); ^ user.cpp:18:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^