#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
using namespace std;

//#define __int64 long long
#define long __int64
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vecy[4] = {0,-1,0,1};
const int Vecx[4] = {1,0,-1,0};

bool check(string s){
	int c1 = 0;
	int c2 = s.length() - 1;
	while(c1 <= c2){
		if(s[c1] != s[c2]){
			return false;
		}
		c1 ++;
		c2 --;
	}
	
	return true;
}

int main(){
	string s;
	string s2;
	cin >> s;
	int c1 = 0;
	int c2 = s.length() - 1;
	
	while(c1 <= c2){
		if(s[c1] != s[c2]){	
			s2 = s;
			s2.insert(s2.begin() + c1, s[c2]);
			if(check(s2)){
				cout << s2 << endl;
				return 0;
			}
			
			s2 = s;
			s2.insert(s2.begin() + c2, s[c1]);
			if(check(s2)){
				cout << s2 << endl;
				return 0;
			}
			
			cout << "NA" << endl;
			return 0;
		}
		
		c1 ++;
		c2 --;
	}
	
	s.insert(s.begin() + s.length() / 2, s[s.length() / 2]);
	cout << s << endl;
		
    
    return 0;
}