Compilare: user.c: In function ‘main’: user.c:17:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("inv.in","r",stdin),freopen("inv.out","w",stdout),scanf("%d",&n); ^ user.c:17:40: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("inv.in","r",stdin),freopen("inv.out","w",stdout),scanf("%d",&n); ^ user.c:17:68: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] freopen("inv.in","r",stdin),freopen("inv.out","w",stdout),scanf("%d",&n); ^ user.c:19:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",a+i); ^