#include <bits/stdc++.h>
using namespace std;
int main()
{
    ios::sync_with_stdio(false);
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n; scanf("%d",&n);
        int arr[n];
        for(int i=0; i<n; scanf("%d",&arr[i]),i++);
        int index=0;
        if(n==1)index=1;
        else if(n==2)index=-1;
        else
        {
            int sum1,sum2,i;
            for( i=1; i<n-1; i++)
            {
                if(index!=0)break;
                int k=i-1, l=i+1;
                sum1=arr[k];
                sum2=arr[l];
                while(k>=0 && l<n)
                {
                    if(sum1>sum2){l++; sum2+=arr[l];}
                    else if(sum1<sum2){k--; sum1+=arr[k];}
                    else {index=i; break;}
                }
            }
            if(sum1!=sum2)index=-1;
            else index=i;
        }
        printf("%d\n",index);
    }

}