m2m.py

n = int(input("Please enter random seed: "))
message = list(raw_input("Please enter message(s): "))
alphabet = list("ABCDEFGHIJKLMNOPQRSTUVWXYZ")

sequence = ""
decoded = ""

while len(sequence) < 1000:
    n = int(str(n * n).replace("0","1")[-4:-1])
    sequence = sequence + str(n)

seqindex = 0

for c in message:
    if c in alphabet:
        decoded += alphabet[(alphabet.index(c)-int(sequence[seqindex]))%(len(alphabet))]
        seqindex += 1
    else:
        decoded += c

print decoded