Bulls and Cows, also known as Cows and Bulls or Pigs and Bulls or Bulls and Cleots.
It is a game with numbers that may date back a century or more. The secret number is consist of 4 different digits. You should try to guess the secret number. With each guess, you will get the matching result. If the matching digits are on their right positions, they are "bulls", if on different positions, they are "cows". Can you guess the number?