#include <bits/stdc++.h>
using namespace std;

pair<string, string> generate(string s){
    int l = 0, r = s.size() - 1;
    while(l < r){
        if(s[l] != s[r]){
            string t1 = s;
            string t2 = s;
            t1.insert(t1.begin() + l, s[r]);
            t2.insert(t2.begin() + r + 1, s[l]);
            return make_pair(t1, t2);
        }
        l++, r--;
    }
    s.insert(s.begin() + s.size() / 2, s[s.size() / 2]);
    return make_pair(s, s);
}

bool f(string s){
    int l = 0, r = s.size() - 1;
    while(l < r){
        if(s[l] != s[r])return false;
        l++, r--;
    }
    return true;
}

int main(void){
    string s;
    cin >> s;
    auto t = generate(s);
    string ans = "NA";
    if(f(t.first))ans = t.first;
    if(f(t.second))ans = t.second;
    cout << ans << '\n';
}