#include <iostream>
#include <algorithm>
using namespace std;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

bool is_palindrome(string s) {
  return equal(s.begin(), s.begin()+s.size()/2, s.rbegin());
}

string solve(string s) {
  int n = s.size();
  if(is_palindrome(s)) {
    if(n & 1) {
      return s.substr(0, n/2) + s[n/2] + s.substr(n/2, n/2+1);
    } else {
      return s.substr(0, n/2) + 'a' + s.substr(n/2, n/2);
    }
  }
  for(int i : range(n/2)) {
    if(s[i] != s[n-1-i]) {
      string t = s.substr(0, i) + s[n-1-i] + s.substr(i, n-i);
      if(is_palindrome(t)) { return t; }
      t = s.substr(0, n-i) + s[i] + s.substr(n-i, i);
      if(is_palindrome(t)) { return t; }
      return "NA";
    }
  }
  return "(ΦωΦ)";
}

int main(void) {
  string s; cin >> s;
  int n = s.size();
  string res = solve(s);
  cout << res << endl;
  return 0;
}