Isometric Z As Yでクリックしたセルの座標を正しく取得する方法

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Tilemaps;

public class TilemapInfo : MonoBehaviour
{
    private int zMax;

    [SerializeField]
    private Tilemap tilemap;

    [SerializeField]
    private TileBase tile;

    // Start is called before the first frame update
    void Start()
    {
        zMax = tilemap.cellBounds.zMax;
        Debug.Log("zMax = " + zMax);

    }

    // Update is called once per frame
    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            GetTopCell();

        }

    }

    // Z座標が高いセルの情報を取得します
    public Vector3Int GetTopCell()
    {
        Vector2 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);

        //Iterate through tile layers starting at the top
        for (int i = zMax; i >= 0; i--)
        {
            Vector3 v = new Vector3(mousePos.x, mousePos.y, i);
            //check cell
            cell = tilemap.WorldToCell(v);
            if (tilemap.HasTile(cell))
            {
                tilemap.SetTile(cell, tile);
                break;
            }
        }

        return cell;
    }
}

    void Start()
    {
        zMax = tilemap.cellBounds.zMax;
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            GetTopCell();

        }

    }

Vector2 mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);

 for (int i = zMax; i >= 0; i--)

Vector3 v = new Vector3(mousePos.x, mousePos.y, i);

cell = tilemap.WorldToCell(v);

            if (tilemap.HasTile(cell))
            {
                tilemap.SetTile(cell, tile);
                break;
            }