#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }

/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

string solve(){
    string res = "NA";
    string S; cin >> S;
    auto check = [](string T){
        string revT = T;
        reverse(revT.begin(),revT.end());
        bool add = false;
        for(int i = 0; i < T.length();i++){
            if(T[i] == revT[i]) continue;
            if(add) return make_pair(false,T);
            add = true;
            T.insert(T.length()-i, string(1,T[i]));
            revT.insert(i, string(1,T[i]));
        }
        return make_pair(true,T);
    };
    auto ret1 = check(S);
    if(ret1.first){
        res = ret1.second;
    }
    reverse(S.begin(),S.end());
    auto ret2 = check(S);
    if(ret2.first){
        res = ret2.second;
        reverse(res.begin(),res.end());
    }
    if(ret1.first || ret2.first){
        if(res.length() == S.length()){
            res.insert(res.length()/2, string(1,res[res.length()/2]));
        }
    }
    return res;
}
int main(void) {
    cin.tie(0); ios_base::sync_with_stdio(false);
    cout << solve() << endl;
    return 0;
}