I'm trying to select a random number from 1 - 4. Here's my script - what's wrong with it? It only gives numbers from 1-3.

var ground : GameObject;
var numberOfBuildings : int = 20;
var numberOfRows : int = 5;
var building1 : GameObject;
var building2 : GameObject;
var building3 : GameObject;
var building4 : GameObject;
var position = Vector3 (10,0,10);
var buildingType = 4;
var zchange = 10;
var nothing : GameObject;

function Start (){

var newObj = Instantiate (ground, Vector3(0,-0.1,0), transform.rotation);
newObj.transform.localScale.z = numberOfBuildings*20;
newObj.transform.localScale.x = numberOfRows*40;

}

function Update () {
if (numberOfBuildings > 0) {

buildingType = Random.Range (1,4);

print (buildingType);

switch (buildingType) {
case (1) :
Instantiate (building1, position, transform.rotation);
position += Vector3 (0,0,zchange);
numberOfBuildings--;
break;

case (2) :
Instantiate (building2, position, transform.rotation);
position += Vector3 (0,0,zchange);
numberOfBuildings--;
break;

case (3) :
Instantiate (building3, position, transform.rotation);
position += Vector3 (0,0,zchange);
numberOfBuildings--;
break;

case (4) :
Instantiate (building4, position, transform.rotation);
position += Vector3 (0,0,zchange);
numberOfBuildings--;
break;

}
}
}

Thanks!