gcd（最大公約數）

gcd(a,b)=gcd(b,a%b) 假設a>b;

#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;
int gcd(int a, int b)
{
    return !b? a:gcd(b,a%b);
}
int main()
{
    int a,b;
    while(scanf("%d%d",&a,&b)!=EOF&&(a+b)){
        printf("%d\n",gcd(a,b));
    }
    return 0;
}