#include <bits/stdc++.h>

typedef long long ll;
typedef unsigned long long ull;

#define FOR(i,a,b) for(int (i)=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define RANGE(vec) (vec).begin(),(vec).end()

using namespace std;


class MrKsAnotherGift
{
public:
    void solve(void)
    {
        string s;
        cin>>s;

        int N = s.length();
        string ans[2];
        bool inserted = false;
        for (int i = 0; i < N/2; ++i)
        {
            if ( s[i] != s[N-1-i] )
            {
                if ( inserted )
                {
                    cout<<"NA"<<endl;
                    return;
                }
                ans[0] = s.substr(0,i) + string(1,s[N-1-i]) + s.substr(i,N);
                ans[1] = s.substr(0,N-1-i) + string(1,s[i]) + s.substr(N-1-i,N);
                inserted = true;
            }
        }
        if ( !inserted )
        {
            cout<<(s.substr(0,N/2) + string(1,'a') + s.substr(N/2,N))<<endl;
            return;
        }
        bool ok[2] = {true,true};
        for (int i = 0; i < N; ++i)
        {
            for (int j = 0; j < 2; ++j)
            {
                if ( ans[i] != ans[N-1-i] )
                    ok[j] = false;
            }
        }
        if ( ok[0] )
            cout<<ans[0]<<endl;
        else if ( ok[1] )
            cout<<ans[1]<<endl;
        else
            cout<<"NA"<<endl;
    }
};

#if 1
int main(int argc, char *argv[])
{
        ios::sync_with_stdio(false);
        auto obj = new MrKsAnotherGift();
        obj->solve();
        delete obj;
        return 0;
}
#endif