Compilare: user.c: In function ‘main’: user.c:5:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("simpla.in", "r", stdin); ^ user.c:6:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("simpla.out", "w", stdout); ^ user.c:7:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld", &a, &b); ^