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())
while t>0:
    t-=1
    n=int(input())
    a=list(map(int,input().strip().split()))
    x=a[0]
    for i in range(n):
        if a[i]!=x:
            d=True
    if(d==True):
        x=max(a)
        print(a.index(x)+1)
    else:
        print(-1)