# -*- coding: utf-8 -*-

def kai(S):
    cnts = 0
    cntf = len(S)-1
    while cnts <= cntf :
        if S[cnts] != S[cntf]:
            return 0
        cnts += 1
        cntf -= 1
    return 1



S = list(raw_input())
if len(S) == 1:
    print "".join(S*2)
    exit()
if kai(S):
    n = len(S) / 2
    S.insert(n ,S[n])
    print "".join(S)
    exit()

cnts = 0
cntf = len(S)-1
while cnts <= cntf :
    if S[cnts] != S[cntf]:
        if S[cnts +1] == S[cntf]:
            S.insert(cntf+1, S[cnts])
            if kai(S):
                print "".join(S)
                exit()
            else:
                print "NA"
                exit()
        elif S[cnts] == S[cntf-1]:
            S.insert(cnts, S[cntf])
            if kai(S):
                print "".join(S)
                exit()
            else:
                print "NA"
                exit()
        else:
            print "NA"
            exit()
    cnts += 1
    cntf -= 1