Compilare: user.cpp: In function ‘int main()’: user.cpp:18:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("zvon.in","r",stdin); freopen("zvon.out","w",stdout); ^ user.cpp:18:63: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("zvon.in","r",stdin); freopen("zvon.out","w",stdout); ^ user.cpp:19:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(scanf("%d",&T);T;T--) ^ user.cpp:20:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] { scanf("%d",&N); ^ user.cpp:23:46: 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); V[X].push_back(Y);} ^