alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
ciphertext = "HMYKZ RWAENH CRFMEFZUGHBKZNG OC DILAENBI ML MRKDELQ I HWMR YNI HIM FAO PBGHAF ECSEFOC HWT YNI FOVQINR OJD HWT TI ESVKOT TBKD TBCQBU AHIRF"

plaintext = ""
words = ciphertext.split(' ')

for word in words:
    for i in range(len(word)):
        if i == 0:
            plaintext += word[i]
        else:
            idxA = alphabet.find(word[i])
            idxB = alphabet.find(word[i - 1])
            idx = (idxA - idxB - 1 + len(alphabet)) % len(alphabet)
            plaintext += alphabet[idx]
    plaintext += " "

print(plaintext)