Compilare: user.cpp: In function ‘int main()’: user.cpp:27:52: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int x,i;freopen ("petsoft.in","r",stdin);freopen ("petsoft.out","w",stdout);scanf("%d\n",&N);for(i=2;i<=N;++i){scanf("%d\n",&x);G[x].push_back(i);}DFS(1);cout << dp[1][0];return 0;} ^ user.cpp:27:87: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int x,i;freopen ("petsoft.in","r",stdin);freopen ("petsoft.out","w",stdout);scanf("%d\n",&N);for(i=2;i<=N;++i){scanf("%d\n",&x);G[x].push_back(i);}DFS(1);cout << dp[1][0];return 0;} ^ user.cpp:27:104: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int x,i;freopen ("petsoft.in","r",stdin);freopen ("petsoft.out","w",stdout);scanf("%d\n",&N);for(i=2;i<=N;++i){scanf("%d\n",&x);G[x].push_back(i);}DFS(1);cout << dp[1][0];return 0;} ^ user.cpp:27:139: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int main(){int x,i;freopen ("petsoft.in","r",stdin);freopen ("petsoft.out","w",stdout);scanf("%d\n",&N);for(i=2;i<=N;++i){scanf("%d\n",&x);G[x].push_back(i);}DFS(1);cout << dp[1][0];return 0;} ^