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 _ in range(t):
    n=int(input())
    arr=list(map(int,input().split()))
    if len(set(arr))==1:
        print(-1)
        continue

    ind=-1
    maxx=0
    for i in range(n):
        if maxx < arr[i]:
            maxx=arr[i]
            ind=i

    print(ind+1)
