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 i10 in range (t):
    n = int(input())
    a = list(map(int, input().split()))
    p = max(a)
    if sum(a) == n * p:
        print(-1)
    else:
        for i in range(n):
            if ((i > 0 and a[i] > a[i -1]) or (i < n- 1 and a[i] > a[i + 1])) and a[i] == p:
                print(i +1)
                break
        
    