Compilare: user.c: In function ‘check’: user.c:12: warning: unused variable ‘j’ user.c: In function ‘read_and_solve’: user.c:27: warning: unused variable ‘k’ user.c:27: warning: unused variable ‘j’ user.c:29: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:30: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c: In function ‘main’: user.c:42: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:43: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:45: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result