#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,b) FOR(i,0,b)
#define F first 
#define S second
#define PB push_back
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;

typedef LL ut;
typedef vector<ut> VI;
const ut INF=1<<30;
const int SIZE=1e+6;
const ut eps=1e-9;
VI primes;

string answer;
bool solve(string str,int s,int e,bool used){
	while(s<=e){
		if(str[s]==str[e]){
			s++;
			e--;
		}
		else{
			if(used) return false;
			if(solve(str,s+1,e,true)){
				str.insert(e+1,string(1,str[s]));
				s++;
			}
			else if(solve(str,s,e-1,true)){
				str.insert(s,string(1,str[e]));
				s++;
			}
			else return false;
			used=true;
		}
	}
	if(!used){
		str.insert((s+e)/2,string(1,str[(s+e)/2]));
	}
	answer=str;
	return true;
}
int main(){
	string s;
	cin >> s;
	int N=s.size();
	if(solve(s,0,N-1,false)) cout << answer<<endl;
	else cout << "NA" << endl;
	return 0;
}