Write a simple program in Java or C, that will help you to figure out the key used for Vigenre encrypted file. For this exercise, assume the key length is less than five characters long and only English upper case letters from A-Z are used. You may also assume the plaintext contains only the upper case English letters from A-Z, ignore the space characters. Your program should take a ciphertext file (encrypted using the Vigenre encryption algorithm) as input and produce an output file where at the first line print the key used for the encryption, followed by a decrypted plaintext in it.