using System;
using System.Collections.Generic;

class Program
{
    static double TinhBieuThucHauTo(string[] bieuThuc)
    {
        Stack<double> stack = new Stack<double>(); 

        foreach (string phanTu in bieuThuc)
        {
            double so;

            if (double.TryParse(phanTu, out so))
            {
                stack.Push(so);
            }
            else
            {
                double toanHang2 = stack.Pop();
                double toanHang1 = stack.Pop();
                double ketQua = 0;

                switch (phanTu)
                {
                    case "+":
                        ketQua = toanHang1 + toanHang2;
                        break;
                    case "-":
                        ketQua = toanHang1 - toanHang2;
                        break;
                    case "*":
                        ketQua = toanHang1 * toanHang2;
                        break;
                    case "/":
                        ketQua = toanHang1 / toanHang2;
                        break;
                    default:
                        Console.WriteLine("Toan tu khong hop le");
                        break;
                }

                stack.Push(ketQua);
            }
        }

        return stack.Pop();
    }

    static void Main()
    {
        string[] bieuThuc = { "2", "3", "4", "*", "+" };

        double ketQua = TinhBieuThucHauTo(bieuThuc);
        Console.WriteLine("Ket qua la: " + ketQua);
    }
}