calculator in notepad

@ECHO OFF
color 0a
title Kalkulator
ECHO www.saznaj-novo.uz.rs
ECHO -----------------------------------------------------
ECHO * = Mnozenje
ECHO + = Sabiranje
ECHO - = Oduzimanje
ECHO / = Djeljenje
:loop
echo.
echo -----------------------------------------------------
ECHO [Ukucaj izraz potom pritisni Enter za rezultat]
SET /p UDefine=
SET /a UDefine=%UDefine%
ECHO =
ECHO %UDefine%
ECHO.
goto loop