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

S = raw_input()
L = len(S)
for i in xrange(L/2):
    if S[i] != S[L-1-i]:
        sol0 = S[:L-i] + S[i] + S[L-i:]
        if is_palindromic(sol0):
            print(sol0)
            quit()
        sol1 = S[:i] + S[L-1-i] + S[i:]
        if is_palindromic(sol1):
            print(sol1)
            quit()
        print('NA')
        quit()
center = S[L/2]
print(S[:L/2] + center + S[L/2:])