(e) {
    return e.ctrlKey && e.keyCode === 83;
}

function isKeyCancel(e) {
    return e.keyCode === 27;
}

function cancelLeftClick() {
    document.addEventListener('click', function (e) {
        if (e.button !== 0) {
            e.preventDefault();
        }
    }, false);
}

function listhead(n) {
    var result = "";
    for (var i = 1; i <= n; i++) {
        result += '<ul>';
    }
    return result;
}

function listfoot(n) {
    var result = "";
    for (var i = 1; i <= n; i++) {
        result += 