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())
    arr = [int(val) for val in input().split(' ')]
    m = max(arr)
    res = -1
    for i in range(n):
        if arr[i] == m and ((i > 0 and arr[i-1] < m) or (i < n-1 and arr[i+1] < m)):
            res = i+1
            break
    print(res)
