Compilare: user.c: In function ‘main’: user.c:20: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:21: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:24: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:26: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:28: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result