#!/usr/bin/python

from sys import argv, stdin

# This will be different for everyone!
# rowlen and rows_per_block form the key
rowlen, rows_per_block = [int(n) for n in argv[1].split("x")]
blocklen = rowlen * rows_per_block

fulltext = stdin.read().lower()

ciphertext = ""
# This operates on one block at a time
block = ""

# Encrypts whatever is in block.
# If the block[row * rowlen + col] doesn't make sense,
# draw a block of numbers on paper, starting at 0, and 
# observe that the formula row*rowlen + col comes out right
# assuming you number rows and columns starting at 0
def encrypt_block():
	encrypted_block = ""
	for col in range(rowlen):
		for row in range(rows_per_block):
			encrypted_block += block[row * rowlen + col]
	return encrypted_block
	
for letter in fulltext:
	letter_number = ord(letter) - ord('a') + 1
	if letter_number < 1 or letter_number > 26:
		continue

	# Fill block with appropriate letters
	block += letter

	if len(block) == blocklen:
		ciphertext += encrypt_block()
		block = ""

# Maybe there was something in block when the end of 
# the ciphertext was reached, and if so, it needs to
# be encrypted.  Think about the implications of using
# the beginning of the ciphertext for padding!
if len(block) > 0:
	block += ciphertext
	ciphertext += encrypt_block()

print ciphertext.upper()