s = raw_input()
n = len(s)
for i in xrange(n / 2):
    if s[i] != s[n-i-1]:
        t = s[:n-i] + s[i] + s[n-i:]
        u = s[:i] + s[-i-1] + s[i:]
        if t == t[::-1]:
            print t
            break
        elif u == u[::-1]:
            print u
            break
        else:
            print "NA"
            break
else:
    print s[:n / 2] + s[n / 2] + s[n / 2:]