C program to convert a binary code to gray code

/*C program to convert a binary code to gray code - */ 
#include <stdio.h>
#include <math.h>

int bintogray(int);

int main ()
{
int bin, gray;

printf("Enter a binary number: ");
scanf("%d", &bin);
gray = bintogray(bin);
printf("The gray code of %d is %d\n", bin, gray);
return 0;
}

int bintogray(int bin)
{
int a, b, result = 0, i = 0;

while (bin != 0)
{
a = bin % 10;
bin = bin / 10;
b = bin % 10;
if ((a && !b) || (!a && b))
{
result = result + pow(10, i);
}
i++;
}
return result;
}