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

def get_dom(a, n):
    mx = max(a)

    for i in range(n):
        if a[i] != mx:
            for j in range(i, -1, -1):
                if a[j] == mx:
                    return j + 1
            for j in range(i, n):
                if a[j] == mx:
                    return j + 1


    return -1



for t in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    print(get_dom(a, n))

