s = list(raw_input())
N = len(s)
is_even = N & 1
H = N >> 1
f = s[:H+is_even]
b = s[-(H+is_even):][::-1]
for i in range(H):
	if f[i] != b[i]:
		if f[i:-1] == b[i+1:]:
			s.insert(i,b[i])
		elif f[i+1:] == b[i:-1]:
			s.insert(N-i,f[i])
		else:
			s = ["NA"]
		break
else:
	s.insert(H,s[H]) 
print "".join(s)