Compilare: user.c: In function ‘perm’: user.c:4:19: warning: unused variable ‘k’ [-Wunused-variable] int i, j, ok, k; ^ user.c: In function ‘main’: user.c:28:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("permutari.in", "r", stdin); ^ user.c:29:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("permutari.out", "w", stdout); ^ user.c:32:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^