1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

t=int(input())
for test in range(t):
    n=int(input())
    arr = list(map(int,input().split()))
    temp=arr[0]
    check=arr.count(temp)
    if check!=n:
        maxx=max(arr)
        print(arr.index(maxx)+1)
    else:
        print(-1)