#include<iostream>

using namespace std;


int main(){

  while(true){
    string s[3];
    cin >> s[0];
    if(s[0] == "0")break;
    cin >> s[1];
    cin >> s[2];
    if(s[0][0] == s[0][1] && s[0][1] == s[0][2] && s[0][0] != '+'){
      cout << s[0][0] << endl;
      continue;
    }
    if(s[0][0] == s[1][0] && s[1][0] == s[2][0] && s[0][0] != '+'){
      cout << s[0][0] << endl;
      continue;
    }
    if(s[0][0] == s[1][1] && s[1][1] == s[2][2] && s[0][0] != '+'){
      cout << s[0][0] << endl;
      continue;
    }
    if(s[0][1] == s[1][1] && s[1][1] == s[2][1] && s[0][1] != '+'){
      cout << s[0][1] << endl;
      continue;
    }
    if(s[0][2] == s[1][2] && s[1][2] == s[2][2] && s[0][2] != '+'){
      cout << s[0][2] << endl;
      continue;
    }
    if(s[0][2] == s[1][1] && s[1][1] == s[2][0] && s[0][2] != '+'){
      cout << s[0][2] << endl;
      continue;
    }
    if(s[1][0] == s[1][1] && s[1][1] == s[1][2] && s[1][0] != '+'){
      cout << s[1][0] << endl;
      continue;
    }
    if(s[2][0] == s[2][1] && s[2][1] == s[2][2] && s[2][0] != '+'){
      cout << s[2][0] << endl;
      continue;
    }


      cout<< "NA" << endl;
  }
  return 0;
}