#include <iostream>
#include <algorithm>
#include <cstdio>
#include <queue>
#include <vector>

using namespace std;

bool isPalin(string s){
    for(int ctr1=0;ctr1<(s.length()+1)/2;ctr1++){
        if(s[ctr1]!=s[s.length()-1-ctr1])
            return false;
    }
    return true;
}

typedef long long ll;

int main()
{
    string s;
    cin>>s;
    for(int ctr1=0;ctr1<(s.length()+1)/2;ctr1++){
        if(s[ctr1]!=s[s.length()-1-ctr1]){
            string t=s;
            string ap;
            ap+=s[s.length()-1-ctr1];
            t.insert(ctr1,ap);
            if(isPalin(t)){
                cout<<t;
                return 0;
            }
            t=s;
            ap=s[ctr1];
            t.insert(s.length()-ctr1,ap);
            if(isPalin(t)){
                cout<<t;
                return 0;
            }
            cout<<"NA";
            return 0;

        }
    }
    string t;
    t+=s[(s.length())/2];
    s.insert(s.length()/2,t);
    cout<<s;
    return 0;
}