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())
    found=0
    ar=list(map(int,input().split()))
    for i in range(1,n):
        if ar[i-1]>ar[i]:
            print(i);found=1
            break
        elif ar[i-1]<ar[i]:
            print(i+1)
            found=1
            break
    if found==0:
        print(-1)
    