Compilare: user.c: In function ‘main’: user.c:28: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:29: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:31: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:38: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:79: warning: control reaches end of non-void function