Quiz works but having a problem with the display, not sure what is wrong

var questions = [
[ "What number comes just before 1?", 0],
["What number is the lowest 3 didget number?", 100],
["Meaning of life?", 42]
]

var correctAnswers = 0;
var question;
var answer;
var response;
var HTML;

var correct = []
var incorrect = []

function print(message) {
  var outputDiv = document.getElementById('output');
  outputDiv.innerHTML=message;
}

function buildList(arr) {
var listHTML = '<ol>';
  for (var i = 0; i < arr.length; i += 1) {
  listHTML += '<li>' + arr[i] + '<li>';
  }
  listHTML += '</ol>';
  return listHTML;
}

for (var i = 0; i < questions.length; i += 1) {
question = questions[i][0];
answer = questions[i][1]
response = parseInt(prompt(question));
  if (response === answer) {
  correctAnswers += 1;
    correct.push(question);
  } else {
    incorrect.push(question);
    }
}

HTML ="You got " + correctAnswers + " answers right!";
HTML +='<h2>You got these questions correct:';
HTML += buildList(correct);
HTML +='<h2>You got these questions wrong<h2>'
HTML += buildList(incorrect);
print(HTML);