public void saveNumber(String s, TreeNode node){
        s += node.val;
        if(node.left == null && node.right ==null){
            total += Integer.parseInt(s);
        }
        else{
            if(node.left != null)
                saveNumber(s,node.left);
            if(node.right != null)
                saveNumber(s,node.right);
        }
    }