How do i Invert Y axis in this Script?

Hi, i am making a third person game and i recently got a camera script which works like a GTA camera and by the way prevents the camera to pass through walls and objects, but i want to invert its Y axis configuration 'cause when i slide the mouse forward, the camera goes up, and when sliding backward, the camera goes down, and i don't like this way. I´m not exactly a programmer (i focus on the visual things) and i wonder if you could help me doing this. The script has some portuguese words (alvo means target and rotacao means rotation) and here it is(thanks for answering):

using UnityEngine; using System.Collections;

public class collisionCamera : MonoBehaviour {

 public Transform alvo;
 RaycastHit hit = new RaycastHit();
 public float mouseX = 0;
 public float mouseY = 0;
 public float distCam = 0;
 
 // Use this for initialization
 void Start () {
     
 }
 
 // Update is called once per frame
 void Update () {
     
     transform.RotateAround (alvo.position, transform.up, Input.GetAxis ("Mouse X") * mouseX);
     transform.RotateAround (alvo.position, transform.right, Input.GetAxis ("Mouse Y") * mouseY);
     
     Vector3 rotacao = transform.eulerAngles;
     rotacao.z = 0;
     transform.eulerAngles = rotacao;
     
     transform.position = alvo.position - transform.forward * distCam;
     
     if(Physics.Linecast(alvo.position, transform.position, out hit))
         transform.position = hit.point+transform.forward*0.4f;
         
         
     }
 }