Compilare: user.cpp: In function ‘int main()’: user.cpp:26:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("darb.in","r",stdin); ^ user.cpp:27:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("darb.out","w",stdout); ^ user.cpp:28:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:29:46: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (i=1;i<=n;i++) {scanf("%d%d", &x, &y); a[x].push_back(y); a[y].push_back(x);} ^