encode = {
	"11":"a",
	"12":"b",
	"13":"c",
	"14":"d",
	"15":"e",
	"21":"f",
	"22":"g",
	"23":"h",
	"24":"i",
	"25":"j",
	"31":"k",
	"32":"l",
	"33":"m",
	"34":"n",
	"35":"o",
	"41":"p",
	"42":"q",
	"43":"r",
	"44":"s",
	"45":"t",
	"51":"u",
	"52":"v",
	"53":"w",
	"54":"x",
	"55":"y",
	"61":"z",
	"62":".",
	"63":"?",
	"64":"!",
	"65":" "
	}

while True:
	try:
		source = raw_input()
	except EOFError:
		break
	
	code = ""
	judge = True
	for i in range(0, len(code), 2):
		if source[i:i+2] in encode:
			code += encode[source[i:i+2]]
		else:
			judge = False
			break
		
	if judge:
		print code
	else:
		print "NA"