// JavaScript Document
  var r1,r2,r3,r4;
  r1 = randomNumber(79)+1;
  r2 = randomNumber(79)+1;
  r3 = randomNumber(79)+1;
  r4 = randomNumber(79)+1;
  checkForDouble();

function randomNumber(limit){
  return Math.floor(Math.random()*limit);
}

function checkForDouble(){
  if (r1==r2 || r1==r3 || r1==r4 || r2==r3 || r2==r4 || r3==r4) newRandomNumbers();
}

function newRandomNumbers(){
//alert("dubbelen gevonden: "+r1+" "+r2+" "+r3+" "+r4+".");
  r1 = randomNumber(78)+1;
  r2 = randomNumber(78)+1;
  r3 = randomNumber(78)+1;
  r4 = randomNumber(78)+1;
  checkForDouble();
}