#include<iostream>
#include<algorithm>
#include<climits>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<string>
#include<cstring>
#include<vector>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<bitset>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;

#define PI 3.141592653589793238462643383279
#define mod 1000000007LL
#define rep(i, n) for(i = 0;i < n;++i)
#define rep1(i, n) for(i = 1;i < n;++i)
#define per(i, n) for(i = n - 1;i > -1;--i)
#define int(x) int x; scanf("%d",&x)
#define int2(x, y) int x, y; scanf("%d%d",&x, &y)
#define int3(x, y, z) int x, y, z; scanf("%d%d%d",&x, &y, &z)
#define int4(v, x, y, z) int v, x, y, z; scanf("%d%d%d%d", &v, &x, &y, &z)
#define int5(v, w, x, y, z) int v, w, x, y, z; scanf("%d%d%d%d%d", &v, &w, &x, &y, &z)
#define ll2(x, y) ll x, y; cin >> x >> y;
#define scn(n, a) rep(i, n)cin >> a[i]
#define sc2n(n, a, b) rep(i, n)cin >> a[i] >> b[i]
#define pri(x) cout << (x) << "\n"
#define pri2(x, y) cout << (x) << " " << (y) << "\n"
#define pri3(x, y, z) cout << (x) << " " << (y) << " " << (z) << "\n"
#define pb push_back
#define mp make_pair
#define all(a) (a).begin(),(a).end()
#define kabe puts("---------------------------")
#define kara puts("")
#define debug(x) cout << " --- " << (x) << "\n"
#define debug2(x, y) cout << " --- " << (x) << " " << (y) << "\n"
#define debug3(x, y, z) cout << " --- " << (x) << " " << (y) << " " << (z) << "\n"
#define X first
#define Y second
#define eps 0.0001
#define prid(x) printf("%.15lf\n", x)

string s[3];
signed main(void){
  int i, j;
  for(int testcase = 0;testcase >= 0;testcase++){
    cin >> s[0] >> s[1] >> s[2];
    if(s[0][0] == '0')break;

    rep(i, 3){
      rep(j, 3)if(s[i][0] != s[i][j])break;
      if(j == 3){
        cout << s[i][0] << endl;
        break;
      }
      rep(j, 3)if(s[0][i] != s[j][i])break;
      if(j == 3){
        cout << s[0][i] << endl;
        break;
      }
    }
    if(i == 3){
      if(s[0][0] == s[1][1] && s[1][1] == s[2][2]){
        cout << s[0][0] << endl;
        continue;
      }
      if(s[0][2] == s[1][1] && s[1][1] == s[2][0]){
        cout << s[0][0] << endl;
        continue;
      }
      puts("NA");
    }



//*/

//*/ break;
  }
  return 0;
}