Compilare: user.c: In function ‘main’: user.c:13: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:14: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:16: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:19: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result