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())
while t:
    t-=1
    n = int(input())
    a = list(map(int, input().split()))
    m = max(a)
    if len(a) == a.count(m):
        print(-1)
    else:
        for i in range(len(a)):
            if i > 0:
                if a[i] == m and a[i] > a[i-1]:
                    print(i+1)
                    break
            if i < n:
                if a[i] == m and a[i] > a[i+1]:
                    print(i+1)
                    break

