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()))

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