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 t in range(T):
    n = int(input())
    A = [int(i) for i in input().split()]
    max_A = max(A)
    ind = []
    for i in range(n):
        if i == 0 and A[i] == max_A and A[i] > A[i+1]:
            print(1)
            break
        elif i == n-1 and A[i] == max_A and A[i] > A[i-1]:
            print(n)
            break
        elif i > 0 and i < n-1 and  A[i] == max_A and (A[i] > A[i-1] or A[i] > A[i+1]):
            print(i+1)
            break
    else:
        print(-1)

