#include <iostream> using namespace std; bool isPalin(const string& s){ const int n = s.size(); for(int i=0;i<n;i++){ if(s[i] != s[n-i-1])return false; } return true; } string solve(const string& s){ const int n = s.size(); if(isPalin(s)){ string front = s.substr(0, n / 2); string back = s.substr(n / 2); return front + back[0] + back; } for(int i=0;i<n;i++){ if(s[i] != s[n-i-1]){ string front = s; front.insert(front.begin() + i, s[n-i-1]); if(isPalin(front))return front; string back = s; back.insert(back.begin() + (n - i - 1) + 1, s[i]); if(isPalin(back))return back; break; } } return "NA"; } int main(){ string s; cin >> s; cout << solve(s) << endl; return 0; }