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 k in range(t):
    n = int(input())
    li = list(map(int, input().split()))
    count = 0
    c = 0
    for i in li:
        if i == li[0]:
            count += 1
    d = max(li)
    flag = False
    for i in range(n):
        if li[i] == d and not flag:
            if i == 0 and (li[i] > li[i + 1]):
                c = i
                flag = True
            elif i == n - 1 and (li[i] > li[i - 1]):
                c = i
                flag = True
            elif i > 0 and i < n - 1:
                if (li[i] > li[i - 1]) or (li[i] > li[i + 1]):
                    c = i
                    flag = True

    if count == n:
        print(-1)
    else:
        print(c + 1)