def is_palindrome(s, lo, hi) -> bool:
    while lo < hi:
        if s[lo] != s[hi]:
            return False
        lo += 1
        hi -= 1

    return True


S = input()


def solve():
    lo = 0
    hi = len(S)-1
    while lo < hi:
        if S[lo] != S[hi]:
            if is_palindrome(S, lo+1, hi):
                t = list(S)
                t.insert(hi+1, S[lo])
                # print(f'lo {t=}')
                if is_palindrome(t, 0, len(t)-1):
                    return ''.join(t)

            if is_palindrome(S, lo, hi-1):
                t = list(S)
                t.insert(lo, S[hi])
                # print(f'hi {t=}')
                if is_palindrome(t, 0, len(t)-1):
                    return ''.join(t)

            return None

        lo += 1
        hi -= 1

    m = len(S) // 2
    t = list(S)
    t.insert(m, S[m])
    return ''.join(t)


ans = solve()
if ans is not None:
    print(ans)
else:
    print('NA')