The main function works as follows:

1. The user is prompted to input their desired action.
2. If the user enters encrypt:
   1. The user is prompted to input their plaintext message.
   2. The message is encrypted (use a rotation_amount of 4)
   3. The plaintext message is hashed to produce a secure value (use 31 as the base and 1000000000 as the hash size).
   4. Both the encrypted message and hash are printed to the user.
3. Otherwise, if the user enters decrypt:
   1. The user is prompted to input their encrypted message.
   2. The message is decrypted (reuse the same rotation_amount from before).
   3. The user is prompted to input the expected hash.
   4. The hash of the decrypted message is compared to the expected hash.
   5. If the hashes are the same, print the decrypted message.
   6. If the hashes are different, your output must include the text “error”.
4. Otherwise, print an error message and exit the app.

Unlike the previous project, we have not provided any imports; you should copy over your existing code from the previous parts.

We are not checking the exact text of what you print to the user, so you are free to make up your own prompts and instructions. However, you must call the input function an appropriate number of times (once to get the user’s chosen action, once more if they encrypt, and twice more if they decrypt). Remember, do not unit test your main function (though of course you should have unit tests for your other functions).