Compilare: user.c: In function ‘main’: user.c:28:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(IN, "r", stdin); ^ user.c:29:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(OUT, "w", stdout); ^ user.c:31:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%llu %llu %llu", &a, &b, &c); ^