Getting CS0117 error ... Help

I'm learning c# scripting and the book i'm following has the same code but it's not running for some reason...so please help me where i'm doing wrong .... Here is the code :-

using UnityEngine; using System.Collections;

public class Input : MonoBehaviour {

 public Vector3 pos;

 // Use this for initialization
 void Start () 
 {
     pos = transform.position;
 
 }
 
 // Update is called once per frame
 void Update () 
 {
     bool aKey = Input.GetKey (KeyCode.A);
     bool dKey = Input.GetKey (KeyCode.D);
     bool wKey = Input.GetKey (KeyCode.W);
     bool sKey = Input.GetKey (KeyCode.S);

             if (aKey)
     {
         pos.x = pos.x - 0.1f;    
     }

     if (dKey) 
     {    
         pos.x = pos.x + 0.1f;
     }

     if (wKey) 
     {
         pos.z = pos.z + 0.1f;
     }

     if (wKey) 
     {
         pos.z = pos.z - 0.1f;
     }

     transform.position = pos;
 }

}

and this is the error :-

Input.cs(20,35): error CS0117: Input' does not contain a definition for GetKey'

Thanks :D