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()))
    m = -179
    check = True
    for i in range(n):
        if a[i] > m:
            m = a[i]
            l = i
            r = i
            check = True
        elif a[i] == m and check:
            r = i
        else:
            check = False
    if a.count(m) == n:
        print(-1)
    elif l != 0 or r == l:
        print(l + 1)
    else:
        print(r + 1)