#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
ll t;
cin>>t;
while(t--)
{
ll n;
cin>>n;
ll A[n];
for(ll i=0;i<n;++i)
{
cin>>A[i];
}
ll result=0;
for(ll k=0;k<n;++k)
{
result = __gcd(A[k],result);
}
if(result==1)
{
cout<<n<<endl;
}
else
cout<<"-1"<<endl;
}
return 0;
}
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