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 i in range(t):
    n = int(input())
    arr = list(map(int, input().split()))
    if len(set(arr)) != 1:
        mm = max(arr)
        for j in range(n - 1):
            if arr[j] == mm and mm != arr[j + 1]:
                print(j + 1)
                break
            elif arr[j] != mm and mm == arr[j + 1]:
                print(j + 2)
                break
    else:
        print(-1)

