Unity Player Movement

using UnityEngine;
using System.Collections;

public class PlayerMovement : MonoBehaviour {
    public float moveSpeed;
    private float maxSpeed = 5f;

    private Vector3 input;

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {
        input = new Vector3 (Input.GetAxisRaw ("Horizontal"), 0, Input.GetAxis ("Vertical"));
        if(rigidbody.velocity.magnitude < maxSpeed)
        {
            rigidbody.AddForce (input * moveSpeed);
        }

    }
}