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

def solve():
    n = int(input())
    a = [int(a) for a in input().split()]
    m = max(a)
    for i,v in enumerate(a):
        if(v==m and ((i > 0 and a[i-1]< v) or (i < n-1 and a[i+1]<v ))):
           print(i+1)
           return
    print(-1)
    return

t = input()
for i in range(int(t)):
   solve()