#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

string S;


int f(string &s){
    int n = sz(s);
    rep(i, n / 2)if(s[i] != s[n - 1 - i])return i;
    return -1;
}

void solve(){
    int N = sz(S), k = f(S);
    string ans, tmp1, tmp2;
    if(k == -1){
        ans = S.substr(0, N/2) + S[N/2] + S.substr(N/2);
    } else{
        char c1 = S[k], c2 = S[N - 1 - k];
        tmp1 = S.substr(0, k) + c2 + S.substr(k);
        tmp2 = S.substr(0, N - k) + c1 + S.substr(N - k);
        if(f(tmp1) == -1)ans = tmp1;
        if(f(tmp2) == -1)ans = tmp2;
    }
    if(ans == "")ans = "NA";
    cout << ans << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    while(cin >> S){
        solve();
    }
}