#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1 << 28;
//constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/

	string s; cin >> s;
	{
		string t; t = s;
		reverse(t.begin(), t.end());
		if (s == t) {
			string res;
			res += s.substr(0, (s.size() + 1) / 2);
			char c = res.back();
			res += c;
			res += s.substr((s.size() + 1) / 2, s.size());
			cout << res << endl;
			return 0;
		}
	}
	for (int i = 0; i < s.size() / 2; i++) {
		if (s[i] != s[s.size() - 1 - i]) {
			{
				string u = s.substr(0, i);
				u += s[s.size() - 1 - i];
				u += s.substr(i, s.size());
				string t = u; reverse(t.begin(), t.end());
				if (u == t) {
					cout << u << endl;
					return 0;
				}
			}
			{
				string u = s.substr(0, s.size() - i);
				u += s[i];
				if(i != 0) u += s.substr(s.size() - i, s.size());
				string t = u; reverse(t.begin(), t.end());
				if (u == t) {
					cout << u << endl;
					return 0;
				}
			}
			cout << "NA" << endl;
			return 0;
		}
	}
	cout << "NA" << endl;
	return 0;
}