Compilare: main.c: In function 'main': main.c:5:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("sum.in","r",stdin),freopen("sum.out","w",stdout),scanf("%d",&t); ^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:5:33: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("sum.in","r",stdin),freopen("sum.out","w",stdout),scanf("%d",&t); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:5:63: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] freopen("sum.in","r",stdin),freopen("sum.out","w",stdout),scanf("%d",&t); ^~~~~~~~~~~~~~ main.c:15:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x),printf("%lld\n",1LL*v[x]*x*2); ^~~~~~~~~~~~~~