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 tc in range(int(input())):
    n = int(input())
    arr = list(map(int, input().split()))
    mx = max(arr)
    for index, val in enumerate(arr):
        if val == mx:
            if index > 0:
                if index < n - 1:
                    if arr[index - 1] < val or arr[index + 1] < val:
                        print(index + 1)
                        break
                else:
                    if arr[index - 1] < val:
                        print(index + 1)
                        break
            else:
                if arr[index + 1] < val:
                    print(index + 1)
                    break
    else:
        print(-1)
