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())
    arr = list(map(int,input().split()))
    arr.append(-1)
    
    domi = -1
    for i in range(n):
        if i == 0 or i == n-1:
            if i == 0 and arr[i] > arr[i+1] and arr[i] > arr[domi]:
                domi = i
            elif i == n-1 and arr[i] > arr[i-1] and arr[i] > arr[domi]:
                domi = i
        elif (arr[i-1] < arr[i] or arr[i] > arr[i+1]) and arr[i] > arr[domi]:
            domi = i
    
    if domi > -1:
        print(domi+1)
    else:
        print(domi)