Compilare: user.c: In function ‘main’: user.c:7:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sieve.in", "r", stdin); ^ user.c:8:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sieve.out", "w", stdout); ^ user.c:23:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", &t); ^ user.c:26:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i", &n); ^