#include<iostream>
#include<algorithm>
#include<set>
#define tip long
using namespace std;
tip t,n,i,a,b,x,sc,j,y,lcm,sol;
int main()
{
    cin>>t;
    for(;t;t--)
    {
        cin>>n>>a;
        sol=0;
        sc=1;
        for(i=2;i<=n;i++)
        {
            cin>>b;
            y=__gcd(a,b);
            if(y!=1){sol=max(sol,sc);sc=1;a=b;continue;;}
            b*=x;
            sc++;
        }
        sol=max(sol,sc);
        if(sol==1||sol==0)sol=-1;
        cout<<sol<<'\n';
    }
    return 0;
}