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 _ in range(int(input())) :
    n = int(input())
    l = list(map(int,input().split()))
    if len(set(l))==1 :
        print(-1)
    else :
        dom = max(l)
        for i in range(n) :
            if l[i]==dom and ((i>0 and l[i-1]<l[i]) or (i<n-1 and l[i+1]<l[i])) :
                print(i+1)
                break

