How to load an array with JsonUtility?

I have a json array :

{ “site”:[[[3,7],[4,6],[5,6],[5,5],[6,5]],[[3,5],[3,5],[4,4],[5,4],[5,4],[6,3]]]}

I try to load:

[System.Serializable]
public class PlayerInfo
{
   [System.Serializable]
    public class PlayerInfo2
    {
        [System.Serializable]
        public class PlayerInfo3
        {
            public int[] id;
        }
        public PlayerInfo3[] site1;

    }
    public PlayerInfo2[] site;
}

But it says like this:

NullReferenceException : Object reference not set to an instance of an object

The JSON you’re representing doesn’t match the model.

If you want to use that model you’d need JSON similar to:

{"site":[{"site1":[{"id":[1,2,3]}]}]}