C# errror "CS0116: A namespace cannot directly contain members such as fields or methods"

Question

I get an error, Assets\scripts\Skins.cs(9,12): error CS0116: A namespace cannot directly contain members such as fields or methods on the Internet they write what it means incorrectly placed brackets, but I don’t see any errors

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

public GameObject choise1;
public GameObject choise2;
public GameObject choise3;

public int skin = 1;

public class Skins : MonoBehaviour {

    void Choise () {
        if (Input.GetMouseDown(choise1)){
            choise2.SetActive (false);
        }
    }
}