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

a = int(input())
for i in range(a):
    fish = int(input())
    arr = list(map(int, input().split(" ")))
    mx = max(arr)
    result = -1
    for j in range(fish):
        if(arr[j]!=mx):
            continue
        if(j>0 and arr[j-1] != mx):
            result = j + 1
        if(j < fish - 1 and arr[j + 1] != mx):
            result = j + 1
    print(result)
        