var eulerQuestions = [];
var questionCount = 0;
var currentAnswer = "?";

function is_correct(answer) {
    if (currentAnswer == "?") {
        alert("Sorry I do not know the answer");
        return;
    }

    var yourHash = md5(answer);
    if (yourHash == currentAnswer) {
        alert('Correct');
    } else {
        alert('Incorrect');
    }
}

function initialize_euler() {
    eulerDb = eulerDb.replace(/(?:rn|r|n)/g, '$NEW');

    var matches;

    var re = /Problems+d+.*?=+(.*?)Answer:s+([a-f0-9]+|?)/g;
    while (matches = re.exec(eulerDb)) {
        eulerQuestions.push([matches[1], matches[2]]);
        questionCount++;
    }

    build_question_buttons();
    render_question(0);
}

function build_question_buttons() {
    var button_temp = '<a onclick="render_question($1);" class="btn btn-default" role="button">$2</a>';
    var generated_html = '';
    for (var i = 0; i < questionCount; i++) {
        var temp_str = button_temp.replace('$1', i);
        temp_str = temp_str.replace('$2', i + 1);
        generated_html += temp_str;
    }

    document.getElementById("questionButtons").innerHTML = generated_html;
}

function render_question(questionId) {
    var question = eulerQuestions[questionId][0].replace(/(?:$NEW)/g, 'n');
    currentAnswer = eulerQuestions[questionId][1];

    if (currentAnswer == "?") {
        question += "nnNote: Answer is not available."
    }
    document.getElementById("question").innerHTML = question;
    document.getElementById("questionNumber").innerHTML = "Problem " + (questionId + 1);

}

<div class="container">
    <div class="container">
        <div class="row well">
            <div class="col-md-4 well well-sm pre-scrollable">
                <div class="btn-toolbar" role="toolbar">
                    <div class="button-container" id="questionButtons">
                    </div>
                </div>
            </div>
            <div class="col-md-8">
                <form role="form" id="questionForm">
                    <div class="form-group">
                        <label id="questionNumber">Problem 01</label>
                    </div>
                    <div class="form-group">
                        <pre id="question" style="">
                        </pre>
                    </div>
                    <div class="form-group">
                        <label>Answer:</label>
                        <input type="text" class="form-control" id="answer">
                    </div>
                        <a class="btn btn-default" role="button" onclick="is_correct(document.getElementById('answer').value)">
                            Test Answer
                        </a>
                </form>
            </div>
        </div>
    </div>
</div>