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 i in range(int(input())):
    n=int(input())
    l=list(map(int,input().split()))
    if l.count(l[0])==n:
        print(-1)
    else:
        a=max(l)
        ans=1
        for j in range(n):
            if l[j]==a and (l[max(0,j-1)]<a or l[min(n-1,j+1)]<a):
                ans=j+1
                break
        print(ans)
