S = input()
L = len(S)


def is_palindrome(s):
    for i in range(len(s) // 2):
        if s[i] != s[len(s) - 1 - i]:
            return False
    return True


if is_palindrome(S):
    print(S[:L // 2] + S[L // 2] + S[L // 2:])
    exit()

for i in range(L // 2):
    if S[i] != S[L - 1 - i]:
        s1 = S[:i] + S[L - 1 - i] + S[i:]
        s2 = S[:L - i] + S[i] + S[L - i:]
        if is_palindrome(s1):
            print(s1)
        elif is_palindrome(s2):
            print(s2)
        else:
            print('NA')
        break