s = list(raw_input())
N = len(s)
H = (N+1)>>1
alf = [chr(97+i) for i in xrange(26)]
for i in xrange(N+1):
	for a in alf:
		s.insert(i,a)
		if s[:H] == s[-H:][::-1]:
			print "".join(s)
			quit()
		s.pop(i)
print "NA"