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

for _ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    m = max(a)

    for i in range(n):
        if i-1 >= 0:
            if a[i-1] != a[i] and a[i] == m:
                print(i+1)
                break

        if i + 1 < n:
            if a[i+1] != a[i] and a[i] == m:
                print(i+1)
                break

        else:
            print(-1)
