#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <list>
#include <queue>
#include <vector>
#include <complex>
#include <set>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) cout<<(p)<<endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////
bool kai(string s){
	
	int Len = s.size();
	for(int i=0;i<Len/2;++i){
		if(s[i] != s[Len-1-i]){
			return false;
		}
	}

	return true;
}
int main(void){
    std::cin.tie(0); 
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    //cout << setprecision(6);//
	
	string s;
	cin>>s;
	int Len = s.size();
	bool odd = false;
	if( (Len+1) %2 == 1){
		odd = true;
	}
	int miss=0;
	string temp;
	for(int i=0; i<Len/2;++i){
		if(s[i] != s[Len-1-i] ){
			temp = s;
			//i-
			temp.insert(i,1,s[Len-1-i]);
			if(kai(temp) == true){
				P(temp);
				return 0;
			}
			temp = s;
			temp.insert(Len-1-i+1,1,s[i]);
			if(kai(temp) == true){
				P(temp);
				return 0;
			}
			P("NA");
			return 0;
		}
	}

	if(odd == true){
		temp = s;
		temp.insert( Len/2,1,'a');
		P(temp);
	}else{
		temp = s;
		temp.insert( (Len/2),1,s[Len/2]);
		P(temp);
	}
    return 0;
}