Compilare: user.c: In function ‘main’: user.c:16: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:17: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:20: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:22: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:25: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:18: warning: ‘k’ may be used uninitialized in this function