#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
using dd = long double;
namespace {
static bool constexpr dbg = 0;
ll constexpr N = -1;
ll n, res;
bool ok(string const &s) {
  ll l = 0, r = s.size() - 1;
  while (l <= r) {
    if (s[l] != s[r]) return false;
    ++l;
    --r;
  }
  return true;
}
void init() {
  string str;
  cin >> str;
  n = str.size();
  string s;
  for (ll i = 0; i <= n; ++i) {
    s = str.substr(0, i) + "?" + str.substr(i);
    for (auto ch = 'a'; ch <= 'z'; ++ch) {
      s[i] = ch;
      if (ok(s)) {
        cout << s;
        return;
      }
    }
  }
  cout << "NA";
}
void solve() {}
void test() {
  if (dbg) {
  }
}
}  // namespace
int main() {
  if (!dbg) {
    std::ios::sync_with_stdio(false);
    cin.tie(nullptr);
  }
  cout << fixed << setprecision(20);
  init();
  solve();
  test();
  return 0;
}
