function LinkedList(value, next) {
    this._value = value;
    this._next = next;
}
LinkedList.prototype.value = function() {
    if (arguments.length == 1) 
        this._value = arguments[0];
    else
        return this._value;
}
LinkedList.prototype.next = function() {
    if (arguments.length == 1) 
        this._next = arguments[0];
    else
        return this._next;
}