viewport Unity3d camera

using UnityEngine;
using System.Collections;

public class Viewtest : MonoBehaviour {

    public Camera cam;

    public float somenum = 0.1f;
    public bool isExpanded = false;
    // Use this for initialization
    void Start () {
        cam = this.GetComponent<Camera> ();
    }

    // Update is called once per frame
    void Update () {
        if (Input.GetKeyDown (KeyCode.UpArrow)){
            isExpanded = !isExpanded;
            cam.rect = new Rect(1f * somenum++ * 0.01f,1f * somenum++ * 0.01f,1f * somenum++ * 0.01f,1f * somenum++ * 0.01f);
        }
        if (Input.GetKeyDown (KeyCode.DownArrow)){
            isExpanded = !isExpanded;
            cam.rect = new Rect(1f * somenum-- * 0.01f,1f * somenum-- * 0.01f,1f * somenum-- * 0.01f,1f * somenum-- * 0.01f);
        }
        if (Input.GetKeyDown (KeyCode.LeftArrow)){
            isExpanded = !isExpanded;
            cam.rect = new Rect(somenum++ * -0.01f,1f * somenum++ * 0.01f,1f * somenum++,1f * somenum++);
        }
        if (Input.GetKeyDown (KeyCode.RightArrow)){
            isExpanded = !isExpanded;
            cam.rect = new Rect(somenum-- * -0.01f,1f * somenum-- * 0.01f,1f * somenum--,1f * somenum--);
        }
    }
}