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 w in range(int(input())):
    n = int(input())
    a = [int(x) for x in input().split()]
    st = set(a)
    b = max(a)
    for i in range(1, n - 1):
        if b == a[i]:
            if a[i - 1] < b or a[i + 1] < b:
                print(i + 1)
                break
    else:
        if (a[0] == b and a[1] < b) :
            print(1)
        elif (a[-1] == b and a[-2] < b):
            print(n)
        else:
            print(-1)