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 = max(a)
    c = a.count(m)
    if c == n:
        ans = -1
    else:
        for i in range(n):
            if a[i] == m:
                if (i - 1 >= 0 and a[i - 1] < m) or (i + 1 < n and a[i + 1] < m):
                    ans = i + 1
                    break
    print(ans)
