#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define REP1(i, n) for(int i=1; i<=(n); i++)
#define RREP1(i, n) for(int i=(n); i>=1; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define out(...) printf(__VA_ARGS__)

int dxy[] = {0, 1, 0, -1, 0};

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/
string s;

bool check(string t) {
    REP(i,t.size()/2) {
        if (t[i] != t[t.size()-1-i]) {
            return false;
        }
    }
    return true;
}

string search() {
    REP(i,s.size()/2) {
        if (s[i] != s[s.size()-1-i]) {
            string t = s;
            t.insert(t.begin() + i, s[s.size()-1-i]);
            if (check(t)) return t;
            string u = s;
            u.insert(u.end()-i, s[i]);
            if (check(u)) return u;
            return "NA";
        }
    }
    // 既に回文
    s.insert(s.begin() + s.size()/2+1, s[s.size()/2]);
    return s;
}

void solve() {
    cin>>s;
    cout << search() << endl;
}