The Cow-Bull game is a famous number and word-guessing game in which at least two player(s) say A and B are involved.

Step 1: A thinks of a number between 1000 and 9999
Step 2: B is expected to guess is correctly
Step 3: B guesses any random number between 1000 and 9999
Step 4: A will give B hints as to how close he is to the answer.
Step 5: If A says B has got a Cow, he means that any particular digit in B's guess is same as in the original number but is not in the correct position.
Step 6: If A says B has got a Bull, he means that any particular digit in B's guess is same as in the original number and is in the correct position.
Step 7: In all, the total number of Cows and Bulls for a particular guess takes B to the next step.

Example:

A thinks of: 6754

B takes a guess: 1564

A says B has got 1 Cow (5) and 1 Bull (4)

Next B guesses 6748

Now B has got 1 Cow (4) and 2 Bulls(6 and 7)



B's aim is to achieve 4 Bulls

In this version, you are B and your phone is A, next version will surely see inter-player challenges, Cheers ! :)