Bulls and cows

Umdlalo we-Classic Code Wreaking lapho kufanele uqagele inombolo enamadijithi amane.

In this game you must guess a 4 digits number, where each digit appears only once.
Each guess you make, it will be displayed the number of digits which are in the right place 'Bulls' represented by the letter B, and the number of digits which are in the number but in another position.

The game 'Mastermind' was inspired by the original version of this game.