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())
res=[]
for i in range(t):
    n = int(input())
    a = list(map(int,input().split()))
    b = set(a)
    if(len(b)>1):
        res.append(a.index(max(a))+1)
    else:
        res.append(-1)
for i in res:
    print(i)