C prob plz help-3-png



Code:
#include <stdio.h>
#include <math.h>
int reverse(int a)
{
 int i=0,j, sum=0, scan;
 scan=a;
 while(a>0)
 {
  a=a/10;
  i++;
 }
 a=scan;
 for(j=0;j<i;j++)
 {
  sum+=(a%(int)pow(10,i-j))/(int)pow(10,i-j-1)*(int)pow(10,j);
 }
 return sum;
}
void main()
{
 int b;
 scanf("%d", &b);
 printf("%d\n", reverse(b));
}
I got the results right, but my professor wants me to finish the program without using math.h header or any functions.

Please help me!