#include <iostream>
#include <string>
using namespace std;
int main(){
  string s1;cin>>s1;
  int ss1=s1.size();
  string ans;
  int cnt=0;
  for(int i=0;i<ss1/2;++i){
    if(ans.size()==0 && cnt==0){
      char a=s1[i];
      char b=s1[ss1-1-i];
      if(a!=b){
        cnt+=1;
        string s2=s1;
        s2.insert(s2.begin()+i,b);
        int ss2=s2.size();
        int f1=0;
        for(int j=i;j<s2.size()/2;++j){
          char c=s2[j];
          char d=s2[s2.size()-1-j];
          if(c!=d){
            f1=1;
            break;
          }
        }
        if(f1==0){
          ans=s2;
        } else {
          string s3=s1;
          s3.insert(s3.end()-i,a);
          int ss3=s3.size();
          int f2=0;
          for(int j=i;j<s3.size()/2;++j){
            char e=s3[j];
            char f=s3[s3.size()-1-j];
            if(e!=f){
              f2=1;
              break;
            }
          }
          if(f2==0) ans=s3;
        }
      }
    } else {
      break;
    }
  }
  if(ans.size()==0 && cnt==0){
    char g=s1[ss1/2];
    s1.insert(s1.begin()+ss1/2,g);
    ans=s1;
  }
  if(ans.size()==0) ans="NA";
  cout<<ans<<endl;
}