#!/usr/bin/env python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


def gen_cand(S):
    L = 0
    R = len(S) - 1
    while True:
        if L == R:
            yield (L, S[L])
            break
        if R == L - 1:
            yield (L, 'a')
            break
        if S[L] != S[R]:
            yield (L, S[R])
            yield (R + 1, S[L])
            break
        else:
            L += 1
            R -= 1


S = list(read().rstrip().decode())
for i, x in gen_cand(S):
    T = S[:]
    T.insert(i, x)
    word = ''.join(T)
    if word == word[::-1]:
        print(word)
        exit()
print('NA')