#include<iostream>
#include<bits/stdc++.h>
using namespace std;
int main()
{
int t; cin>>t;
while(t>0)
{
int n; cin>>n;
int a=0,b=0,s=INT_MAX,p;
for(int i=0;i<n;i++)
{
cin>>p;
if(p==1)a=1;
if((p!=1 && p%2!=0)||p==2)
{
b=p;
if(b<s)
s=b;
}
}
if(a==1)
cout<<s<<"\n";
else
cout<<-1<<"\n";
t--;
}
}
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