Compilare: user.cpp: In function ‘void prim(int)’: user.cpp:12:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<g[s].size(); i++) ^ user.cpp:28:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<g[s].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:41:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("lazy.in","r",stdin); ^ user.cpp:42:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("lazy.out","w",stdout); ^ user.cpp:45:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:48:43: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %lld %lld",&t1,&t2,&t3,&t4); ^