Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:25:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v[node].size();i++) if(!used[v[node][i].to]) { ^ user.cpp: In function ‘int main()’: user.cpp:35:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reconst.in","r",stdin); ^ user.cpp:36:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("reconst.out","w",stdout); ^ user.cpp:40:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:42:40: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld %lld %lld", &a, &b, &c); ^