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())
    x=list(map(int,input().split()))
    idx = x.index(max(x))
    if idx ==0:
        for i in range(1,len(x)):
            if x[i]!=x[0]:
                print(i)
                break
        else:
            print(-1)
    else:
        print(idx+1)
