How to use Armstrong number in C Language

#include <stdio.h>
int main(void)
{
  int num, n, cube, d, sum;
  printf("Armstorng Numbers are :\n");
  for (num = 100; num <= 999; num++)
  {
      n = num;
      sum = 0;
      while (n > 0)
      {
          d = n % 10;
          n /= 10;
          cube = d * d * d;
          sum = sum + cube;
      }
      if (num == sum)
          printf("%d\n", num);
  }
  return 0;
}

Armstrong Number are :
153
370
371
407