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=eval(input())

for j in range(t) :
    n=eval(input())
    a=list(map(int,input().split()))
    m=max(a)
    ctr=-1
    for i in range(0,n) :
        if a[i]==m and ((i>0 and a[i]>a[i-1]) or (i<n-1 and a[i]>a[i+1])) :
            ctr=i+1
    print (ctr)
   