#yuki238

s=raw_input()
n=len(s)
for i in range(n/2):
 if s[i]!=s[n-i-1]:
  t=s[:n-i]+s[i]+s[n-i:]
  u=s[:i]+s[n-i-1]+s[i:]
  if t==t[::-1]:
   print t
  elif u==u[::-1]:
   print u
  else:
   print'NA'
  break
else:
 print s[:n/2]+s[n/2]+s[n/2:]