using System;

using System.Collections.Generic;       

public class Node

{

    public char c;

    public Node left, right;

    public Node(char cc)

    {

        c=cc;

        left=right=null;

    }

}

public class Program

{

    Boolean isOp(char c)

    {

        if(c=='-' || c=='+' || c=='/' || c=='*')

            return true;

        return false;

    }

    Node notation(string s)

    {

        Node t, t1, t2;

        Stack<Node> st = new Stack<Node>();

        for(int i=0; i<s.Length; i++)

        {

            t = new Node(s[i]);

            if(!isOp(s[i]))

                st.Push(t);

            else

            {

                t1=st.Pop();

                t2=st.Pop();

                t.left=t2;

                t.right=t1;

                st.Push(t);

            }

        }

        t = st.Pop();

        return t;

    }

    void inOrder(Node root)

    {

        if(root==null)return;

        inOrder(root.left);

        Console.Write(root.c+" ");  

        inOrder(root.right);

    }

    public static void Main()

    {

        Program tree = new Program();

        String postfix = "ab+ef*g*-";

        Node root = tree.notation(postfix);

        tree.inOrder(root);

    }

}