Compilare: user.c: In function ‘main’: user.c:11:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.in", "r", stdin); ^ user.c:12:9: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.out", "w", stdout); ^ user.c:13:7: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &t); ^ user.c:16:8: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s\n", s); ^