Input class is not working

I imported an asset package and am using it in my project. The scripts are giving me an error for the Input class, none of its functions are being recognised. E.g. Input.GetAxis("Mouse X"), it says " 'Input' does not contain a definition for 'GetAxis' ". I don't understand why this is happening when I am using UnityEngine and System.Collections

 

Are you certain you don't have another class named Input? If so, it could be getting which one to use confused.