function ListNode(val, next) {
    this.val = (val === undefined ? 0 : val)
    this.next = (next === undefined ? 0 : next)
}

var TEST = function () {
    
    function _getNum(node) {
        let str = '';
        while (node !== 0) {
            str += node.val;
            node = node.next;
        }
        return parseInt(str) || 0;
    }
    
    function _getNode(str) {
        let node = 0;
        for (var i=str.length-1; i>=0; --i) {
            node = new ListNode(str[i], node);
        }
        return node;
    }
    
    return {
        exec: function (l1, l2) {
            return _getNode(_getNum(l1) + _getNum(l2) + '');
        }
    };
}();