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()]

    mx = max(A)
    idxs = []
    for i in range(n):
        if A[i] == mx:
            idxs.append(i)
    ans = -1
    for index in idxs:
        if index - 1 >= 0:
            if A[index] > A[index-1]:
                ans = index
                break
        if index + 1 < n:
            if A[index] > A[index+1]:
                ans = index
                break

    if ans != -1:
        print(ans+1)
    else:
        print(-1)
