Compilare: user.c: In function ‘main’: user.c:29:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("twoton.in", "r", stdin); ^ user.c:30:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("twoton.out", "w", stdout); ^ user.c:31:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.c:34:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i]); ^