裴蜀定理

#include <bits/stdc++.h>

using namespace std;

int gcd(int x,int y){
    return y?gcd(y,x%y):x;
}


int main()
{
    int n;
    cin >> n;
    for(int i = 1,x,ans = 0; i <= n ; i ++ )
    {
        cin >> x;
        if(x < 0) x = -x;
        ans = gcd(ans,x);
        if(i == n)cout << ans;
    }

}