#!/usr/bin/env python3
# -*- coding: utf-8 -*-

NO_SOLUTION = "-1"


def is_palindromic(s):
    return s == s[::-1]


def generate_palindrome(s):
    s_len = len(s)
    if is_palindromic(s):
        mid_idx = s_len // 2
        return s[:mid_idx] + s[mid_idx] + s[mid_idx:]
    for i in range(s_len):
        j = s_len - 1 - i
        c_left = s[i]
        c_right = s[j]
        if c_left == c_right:
            continue
        cand1 = s[:j + 1] + c_left + s[j + 1:]
        cand2 = s[:i] + c_right + s[i:]
        for cand in (cand1, cand2):
            if is_palindromic(cand):
                return cand
        return NO_SOLUTION


def main():
    answer = generate_palindrome(input())
    print(answer if answer != NO_SOLUTION else "NA")


if __name__ == '__main__':
    main()