def isKaibun(S):
    L = (len(S) >> 1) + 1
    return all(S[i] == S[len(S) - i - 1] for i in range(L))


def solve(S):
    L = (len(S) >> 1)

    if isKaibun(S):
        print(S[:L] + S[L] + S[L:])
        return

    L += 1

    for i in range(L):
        j = len(S) - i - 1
        if S[i] != S[j]:
            a1 = S[:i] + S[j] + S[i:]
            a2 = S[:j + 1] + S[i] + S[j + 1:]

            if isKaibun(a1):
                print(a1)
            elif isKaibun(a2):
                print(a2)
            else:
                print('NA')
            return


def main():
    S = input()
    solve(S)


if __name__ == '__main__':
    main()