#include <stdlib.h>
#include <stdio.h>

int GCD(int left, int right);
int main(void)
{    
 unsigned int max = 0;
   unsigned int min = 0;
// printf("input:");

while(scanf("%d%d",&max,&min)==2)
 printf("%d",GCD(max,min));

 return 0;

}

int GCD(unsigned int left,unsigned int right)
{
 unsigned int temp = 0;
 
 if (left<right)
 {
  temp = left;
  left = right;
  right = temp;
 }

 if((left%right) ==0)
 {
  return right;
 }

 GCD(right,(left%right));

}

為什麼不行...