n = int(input())
arr = list(map(int, input(). split()))
ans = min(arr)
for i in arr:
if i % ans:
ans = -1
break
print(ans)
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
int main(){
ll n; cin>>n;
ll a[n],x;
for(ll i=0;i<n;i++){
cin>>a[i];
if(i==0) x=a[i];
else x=__gcd(x,a[i]);
}
for(ll i=0;i<n;i++){
if(x==a[i]){
cout<<x; return 0;
}
}
cout<<"-1";
}
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