I am getting following error in Unity error CS0101: The namespace `global::' already contains a definition for `RotateAround', InvalidOperationException: Operation is not valid due to the current state of the object

The screen shot of my error

my script which I am getting error

using UnityEngine;
using System.Collections;

public class RotateAround : MonoBehaviour {

public Transform target; // the object to rotate around
public int speed; // the speed of rotation

void Start() {
	if (target == null) 
		target = this.gameObject.transform;
		Debug.Log ("RotateAround target not specified. Defaulting to parent GameObject");

// Update is called once per frame
void Update () {
	// RotateAround takes three arguments, first is the Vector to rotate around
	// second is a vector that axis to rotate around
	// third is the degrees to rotate, in this case the speed per second
	transform.RotateAround(target.transform.position,target.transform.up,speed * Time.deltaTime);


Use a different name for your class as RotateAround() already exists in Transform.