/* {{{ Shinobu kawaii */
/*
  ______   __        _                  __                 
.' ____ \ [  |      (_)                [  |                
| (___ \_| | |--.   __   _ .--.   .--.  | |.--.   __   _   
 _.____`.  | .-. | [  | [ `.-. |/ .'`\ \| '/'`\ \[  | | |  
| \____) | | | | |  | |  | | | || \__. ||  \__/ | | \_/ |, 
 \______.'[___]|__][___][___||__]'.__.'[__;.__.'  '.__.'_/ 
                                                           
*/
/* }}} */

#include <bits/stdc++.h>
using namespace std;

// #define int long long

/* cpp template {{{ */

/* short */
#define pb push_back
#define mp make_pair
#define print(x) cout << x << '\n'
#define Fi first
#define Se second

/* REPmacro */
#define REPS(i, a, n) for (int i = (a); i < (n); i++)
#define REP(i, n) for (int i = 0; i < (n); i++)
#define RREP(i, n) for (int i = 1; i <= (n); i++)
#define DEPS(i, a, n) for (int i = (a); i >= n; i--)
#define DEP(i, n) for (int i = (n); i >= 0; i--)

/* typedef */
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int> > vii;
typedef pair<int, int> pii;

/* const */
const int INF = 999999999;
const double EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool is_uruu(int y) {return y % 4 == 0 && y % 100 != 0 || y % 400 == 0;}
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}

/* }}} */

signed main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);
  string s[3];

  while (cin >> s[0], s[0] != "0"){
    cin >> s[1] >> s[2];
    bool flg = true;
    REP(i, 3){
      if (s[0][i] == s[1][i] && s[0][i] == s[2][i]){
        print(s[0][i]);
        flg = false;
        break;
      }
    }
    if (flg){
      REP(i, 3){
        if (s[i][0] == s[i][1] && s[i][0] == s[i][2]){
          print(s[i][0]);
          flg = false;
          break;
        }
      }
    }
    if (flg){
      if (s[0][0] == s[1][1] && s[0][0] == s[2][2]){
        print(s[0][0]);
        flg = false;
      }
    }
    if (flg){
      if (s[0][2] == s[1][1] && s[0][2] == s[2][0]){
        print(s[0][2]);
        flg = false;
      }
    }
    if (flg){
      print("NA");
    }
  }

  return 0;
}