Compilare: user.c: In function ‘main’: user.c:20: warning: implicit declaration of function ‘atoi’ user.c:13: warning: unused variable ‘last’ user.c:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:6: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:15: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:17: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result