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 _ in range(t):
    n = int(input())
    A = list(map(int,input().split()))
    m = max(A)
    for i,a in enumerate(A):
        if a == m:
            if i-1 >= 0 and A[i-1] < A[i]:
                print(i+1)
                break
            if i+1 < n and A[i+1] < A[i]:
                print(i+1)
                break
    else:
        print(-1)