function randomNum(max) {
    var rNum=NaN
    while (isNaN(rNum)) {
      rNum=Math.floor(Math.random()*(max))
    }
    return rNum
  }

  var pic = new Array()
//  pic[0]="images/c_image1.jpg"
  pic[0]="images/c_image2.jpg"
//  pic[2]="images/c_image3.jpg"
//  pic[3]="images/c_image4.jpg"
//  pic[1]="images/c_image5.jpg"