using System;
using System.Collections.Generic;
using System.Linq;

namespace Simple_Calculator
{
    class SimpleCalculator
    {
        static void Main(string[] args)
        {
            Stack<string> calc = new Stack<string>(Console.ReadLine().Split(' ', StringSplitOptions.RemoveEmptyEntries).Reverse());

            while (calc.Count > 1)
            {
                int oper1 = int.Parse(calc.Pop());
                string action = calc.Pop();
                int oper2 = int.Parse(calc.Pop());

                if (action.Equals("+"))
                {
                    calc.Push((oper1 + oper2).ToString());
                }
                else if (action.Equals("-"))
                {
                    calc.Push((oper1 - oper2).ToString());
                }
            }

            Console.WriteLine(calc.Pop());
        }
    }
}