There is no problem in compiling and connecting, and there is no result in running

#include <stdio.h>int main(){ char a[16]; int i, b, c; Out:printf(" Please enter the student number :"); for (i = 0; (a[i] = getchar()) != '\n'; i++); if (i != 12) goto Out; c = (a[0] - '0') * 1000 + (a[1] - '0') * 100 + (a[2] - '0') * 10 + a[3] - '0'; if (c < 2018 || c>2021) goto Out; //..... Source code  //..... return 0;}