#
# convert ASCII representation of bytes to bytes
# each pair of characters input represents a byte
# all white space ignored
#
import sys
import string

#
# quit on something bad
# with an error message and exit code
#
# str = error message to be printed
#
def goodbye(str):
	print(str)
	sys.exit(1)

#
# convert character representation of hex digit to a hex digit
# return - if you're given a non-hex digit
#
def cvthex(c):
	return(string.hexdigits.find(c))

#
#############################################
# MAIN ROUTINE
#
# line number of input for error purposes
#
lineno = 0

#
# loop until EOF, then quit
#
while True:
	#
	# read in a line
	# not error handling
	#
	try:
		# read something
		line = input('')
	except EOFError:
		# nothing more to read
		break
	except:
		# something else happened
		goodbye("Could not read input")
	#
	# now process the line
	# should be of the form xx xx xx xx . . .
	# where xx are 2 hex digits; bomb if not
	#
	# at a new line
	lineno += 1
	# break the line up into pairs
	listch = line.split(' ')
	# process each pair
	for i in listch:
		if len(i) != 2:
			# not a pair -- complain and stop
			goodbye("line {0}: sequence {1} not 2 long".format(lineno, i))
		else:
			# convert each char to a hex value
			c0 = cvthex(i[0])
			c1 = cvthex(i[1])
			# complain if given a non-hex digit char
			if c0 == -1 or c1 == -1:
				goodbye("line {0}: non-hex digit in {1}".format(lineno, i))
			# its good -- create the corresponding byte
			else:
				actualch = c0 * 16 + c1
		# now write it to the output
		print("{0:c}".format(actualch), end='')