'OVRInput' could not be found

Please this error is driving me INSANE!! And I can't figure out how does it work. I know there are millions of topics, but there are no explanations and all are different.

This is my case:

 Assets/OvrAvatar/Scripts/OvrAvatarLocalDriver.cs(15,36): error CS0246: The type or namespace name `OVRInput' could not be found. Are you missing an assembly reference?

 using UnityEngine;
 using System.Collections;
 using System;
 using System.Collections.Generic;
 using Oculus.Avatar;
 using UnityEngine.UI;
 
 
 public class OvrAvatarLocalDriver : OvrAvatarDriver {
 
     private const float mobileBaseHeadHeight = 1.7f;
 
     float voiceAmplitude = 0.0f;
     ControllerPose  GetControllerPose(OVRInput.Controller controller)
     {
         ovrAvatarButton buttons = 0;
         if (OVRInput.Get(OVRInput.Button.One, controller)) buttons |= ovrAvatarButton.One;
         if (OVRInput.Get(OVRInput.Button.Two, controller)) buttons |= ovrAvatarButton.Two;
         if (OVRInput.Get(OVRInput.Button.Start, controller)) buttons |= ovrAvatarButton.Three;
         if (OVRInput.Get(OVRInput.Button.PrimaryThumbstick, controller)) buttons |= ovrAvatarButton.Joystick;
 
         ovrAvatarTouch touches = 0;
         if (OVRInput.Get(OVRInput.Touch.One, controller)) touches |= ovrAvatarTouch.One;
         if (OVRInput.Get(OVRInput.Touch.Two, controller)) touches |= ovrAvatarTouch.Two;
         if (OVRInput.Get(OVRInput.Touch.PrimaryThumbstick, controller)) touches |= ovrAvatarTouch.Joystick;
         if (OVRInput.Get(OVRInput.Touch.PrimaryThumbRest, controller)) touches |= ovrAvatarTouch.ThumbRest;
         if (OVRInput.Get(OVRInput.Touch.PrimaryIndexTrigger, controller)) touches |= ovrAvatarTouch.Index;
         if (!OVRInput.Get(OVRInput.NearTouch.PrimaryIndexTrigger, controller)) touches |= ovrAvatarTouch.Pointing;
         if (!OVRInput.Get(OVRInput.NearTouch.PrimaryThumbButtons, controller)) touches |= ovrAvatarTouch.ThumbUp;
 
         return new ControllerPose
         {
             buttons = buttons,
             touches = touches,
             joystickPosition = OVRInput.Get(OVRInput.Axis2D.PrimaryThumbstick, controller),
             indexTrigger = OVRInput.Get(OVRInput.Axis1D.PrimaryIndexTrigger, controller),
             handTrigger = OVRInput.Get(OVRInput.Axis1D.PrimaryHandTrigger, controller),
             isActive = (OVRInput.GetActiveController() & controller) != 0,
         };
     }
 
     private PoseFrame GetCurrentPose()
     {
         Vector3 headPos = UnityEngine.VR.InputTracking.GetLocalPosition(UnityEngine.VR.VRNode.CenterEye);
 #if UNITY_ANDROID && !UNITY_EDITOR
         headPos.y += mobileBaseHeadHeight;
 #endif
 
         return new PoseFrame
         {
             voiceAmplitude = voiceAmplitude,
             headPosition = headPos,
             headRotation = UnityEngine.VR.InputTracking.GetLocalRotation(UnityEngine.VR.VRNode.CenterEye),
             handLeftPosition = OVRInput.GetLocalControllerPosition(OVRInput.Controller.LTouch),
             handLeftRotation = OVRInput.GetLocalControllerRotation(OVRInput.Controller.LTouch),
             handRightPosition = OVRInput.GetLocalControllerPosition(OVRInput.Controller.RTouch),
             handRightRotation = OVRInput.GetLocalControllerRotation(OVRInput.Controller.RTouch),
             controllerLeftPose = GetControllerPose(OVRInput.Controller.LTouch),
             controllerRightPose = GetControllerPose(OVRInput.Controller.RTouch),
         };
     }
 
     public override void UpdateTransforms(IntPtr sdkAvatar)
     {
         if (sdkAvatar != IntPtr.Zero)
         {
             PoseFrame pose = GetCurrentPose();
 
             ovrAvatarTransform bodyTransform = OvrAvatar.CreateOvrAvatarTransform(pose.headPosition, pose.headRotation);
             ovrAvatarHandInputState inputStateLeft = OvrAvatar.CreateInputState(OvrAvatar.CreateOvrAvatarTransform(pose.handLeftPosition, pose.handLeftRotation), pose.controllerLeftPose);
             ovrAvatarHandInputState inputStateRight = OvrAvatar.CreateInputState(OvrAvatar.CreateOvrAvatarTransform(pose.handRightPosition, pose.handRightRotation), pose.controllerRightPose);
 
             CAPI.ovrAvatarPose_UpdateBody(sdkAvatar, bodyTransform);
             CAPI.ovrAvatarPose_UpdateHands(sdkAvatar, inputStateLeft, inputStateRight);
         }
     }
 }

Why?? Please explain the theory behind it! Thanks!