public int sum(TreeNode root, int top)
		{
			if (root == null) return top;
			if (root.left == null && root.right == null)
			{
				return top * 10  + root.val;
			}
			int sum = 0;
			if (root.left != null) sum += sum(root.left, top * 10 + root.val);
			if (root.right != null) sum +=  sum(root.right, top * 10 + root.val);
			return sum;
		}