#include <stdio.h>

int gcd(int, int);

int main(void) {
  int i, j, small, large;
 
  printf("Enter two positive integers: ");
  scanf("%d %d", &i, &j);

  small = i <= j ? i : j;
  large = i <= j ? j : i;
  
  printf("GCD of %d and %d is %d\n\n", i, j, gcd(large, small));
  
  return 0;
}

int gcd(int large, int small){
  int remainder; 
  while (small > 0){
    remainder = large % small;
    large = small;
    small = remainder;
  }
  return large;
}