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 = input().split(' ')
    m = max(p)
    ind = -1
    for j in p:
        if j != m:
            continue
        if p.index(j) > 0 and p[p.index(j)-1] != m:
            ind = p.index(j)+1
        if p.index(j) < n-1 and p[p.index(j)+1] != m:
            ind = p.index(j) + 1
    print(ind)





