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(0,int(input())):
    n =int(input())
    a = list(map(int, input().split()))
    if len(set(a)) == 1:
        print(-1)
    else:
        m = max(a)
        for i in range(0, n):
            if  a[i] == m and ((i!=0 and a[i] > a[i-1]) or a[i] > a[i+1]):
                  print(i+1)
                  break