欧几里得解题10秒一题：

#include<iostream>
#define int long long
int gcd(int a,int b){
    return b==0?a:gcd(b,a%b);
}
signed main(){
    int a,b,c;
    scanf("%d%d%d",&a,&b,&c);
    int ab=gcd(a,b);
    printf("%d",gcd(ab,c));
    return 0;
}