s = raw_input()
m = len(s) / 2
for i in xrange(m):
    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[:m] + s[m] + s[m:]