Compilare: user.c:5:1: warning: return type defaults to ‘int’ [enabled by default] main(){ ^ user.c: In function ‘main’: user.c:7:8: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sumdiv2.in", "r", stdin); ^ user.c:8:8: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen("sumdiv2.out", "w", stdout); ^ user.c:21:6: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &T); ^ user.c:25:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &a); ^ user.c:26:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &b); ^