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()))
    maxA = max(A)
    ans = -2
    for i, a in enumerate(A):
        if a == maxA:
            if i and A[i - 1] < a or i < n - 1 and A[i + 1] < a:
                ans = i
                break
    print(ans + 1)