If entering collision add 1 to a byte wont work

Im getting these errors and dont understand why: Assets/My Scripts/Contact.cs(18,17): error CS1525: Unexpected symbol `}' Assets/My Scripts/Contact.cs(21,1): error CS8025: Parsing error

 using UnityEngine;
 using System.Collections;
 
 public class Contact : MonoBehaviour {
 
     // Use this for initialization
     void Start () 
     {
     
     }
     byte jump = 1;
     // Update is called once per frame
     void OnCollisionEnter(Collision collision)
     {
         if (jump < 1 )
         {
             jump +++
         }
     }
 }