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 i in range(t):
    n = int(input())
    p = list(map(int, input().split()))
    mx = max(p)
    ans = -1
    for i in range(n):
        if p[i] == mx and (i > 0 and p[i - 1] < mx or i < n - 1 and p[i + 1] < mx):
            ans = i + 1
            break
    print(ans)