Restrict 2d drag camera movement

Hi i got this script:

 using UnityEngine;
 using System.Collections;
 
 public class CameraMovement : MonoBehaviour {
     private float dist;
     private Vector3 v3OrgMouse;
     private Plane plane = new Plane(Vector3.up, Vector3.zero);
 
     void Start() {
         dist = transform.position.z;  // Distance camera is above map
     }
 
     void Update() {
 
         if (Input.GetMouseButtonDown(0)) {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             float dist;
             plane.Raycast(ray, out dist);
             v3OrgMouse = ray.GetPoint(dist);
             v3OrgMouse.z = 0;
         } else if (Input.GetMouseButton(0)) {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             float dist;
             plane.Raycast(ray, out dist);
             Vector3 v3Pos = ray.GetPoint(dist);
             v3Pos.z = 0;
             transform.position -= (v3Pos - v3OrgMouse);
         }
     }
 }

I need borders, i tried something like this:

 if (transform.position.x >= -320 && transform.position.y <= 180 && transform.position.x <= 320 && transform.position.y >= -180) {
                 transform.position -= (v3Pos - v3OrgMouse);
             }

But with my script i can move the camera for example to x = -321 and then i cant move anything anymore because the if statement is false.

I hope you have a solution. Thx