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 t in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    a_max = max(a)
    index = None
    i = 0
    while i < n and not index:
        if a[i] == a_max:
            if i - 1 >= 0 and a[i - 1] < a[i]:
                index = i
            if i + 1 < n and a[i + 1] < a[i]:
                index = i
        i += 1

    print(index + 1 if index != None else -1)
                
