So, what's the problem with this code?

Hey guys, I came across this script on the official unity page (http://docs.unity3d.com/ScriptReference/Renderer-material.html) and when pasted into MonoDevelop, I get this error:

Assets/example.cs(11,21): error CS0266: Cannot implicitly convert type float' to int'. An explicit conversion exists (are you missing a cast?)

Can anyone help me solve this problem? This is the script below:

 using UnityEngine;
 using System.Collections;
 
 public class ExampleClass : MonoBehaviour {
     public Material[] materials;
     public float changeInterval = 0.33F;
     void Update() {
         if (materials.Length == 0)
             return;
         
         int index = Time.time / changeInterval;
         index = index % materials.Length;
         renderer.sharedMaterial = materials[index];
     }
 }