Compilare: user.c: In function ‘main’: user.c:11: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:14: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:16: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:13: warning: ‘end’ may be used uninitialized in this function user.c:13: warning: ‘beg’ may be used uninitialized in this function user.c:13: warning: ‘idx’ may be used uninitialized in this function