using System;
using System.Collections.Generic;

class InfixToPostfix
{

    static int Precedence(char op)
    {
        switch (op)
        {
            case '+':
            case '-':
                return 1;
            case '*':
            case '/':
                return 2;
            case '^':
                return 3;
            default:
                return 0;
        }
    }

   
    static bool IsOperator(char c)
    {
        return c == '+' || c == '-' || c == '*' || c == '/' || c == '^';
    }

 
    public static string Convert(string infix)
    {
        Stack<char> stack = new Stack<char>();
        string postfix = "";

        for (int i = 0; i < infix.Length; i++)
        {
            char c = infix[i];

    
            if (c == ' ')
                continue;


            if (Char.IsLetterOrDigit(c))
            {
                postfix += c;
            }
            else if (c == '(')
            {
                stack.Push(c);
            }

            else if (c == ')')
            {
                while (stack.Count > 0 && stack.Peek() != '(')
                {
                    postfix += stack.Pop();
                }
                if (stack.Count > 0 && stack.Peek() == '(')
                    stack.Pop(); // Bỏ dấu '('
            }

            else if (IsOperator(c))
            {
                while (stack.Count > 0 && Precedence(stack.Peek()) >= Precedence(c))
                {
                    postfix += stack.Pop();
                }
                stack.Push(c);
            }
        }
        while (stack.Count > 0)
        {
            postfix += stack.Pop();
        }

        return postfix;
    }

    static void Main()
    {
        Console.Write("Nhap bieu thuc infix: ");
        string infix = Console.ReadLine();
        string postfix = Convert(infix);
        Console.WriteLine("bieu thuc postfix: " + postfix);
    }
}