Compilare: user.c: In function ‘main’: user.c:16:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(fin, "r", stdin); ^ user.c:17:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(fout, "w", stdout); ^ user.c:19:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lu %lu", &a, &b); ^