// 2011/03/01 Tazoe

#include <iostream>
#include <string>
using namespace std;

int main()
{
	while(true){
		string brd[3];
		cin >> brd[0];
		if(brd[0]=="0")
			break;

		cin >> brd[1];
		cin >> brd[2];

		if(brd[0][0]!='+'&&brd[0][0]==brd[0][1]&&brd[0][1]==brd[0][2])
			cout << brd[0][0] << endl;
		else if(brd[1][0]!='+'&&brd[1][0]==brd[1][1]&&brd[1][1]==brd[1][2])
			cout << brd[1][0] << endl;
		else if(brd[2][0]!='+'&&brd[2][0]==brd[2][1]&&brd[2][1]==brd[2][2])
			cout << brd[2][0] << endl;
		else if(brd[0][0]!='+'&&brd[0][0]==brd[1][0]&&brd[1][0]==brd[2][0])
			cout << brd[0][0] << endl;
		else if(brd[0][1]!='+'&&brd[0][1]==brd[1][1]&&brd[1][1]==brd[2][1])
			cout << brd[0][1] << endl;
		else if(brd[0][2]!='+'&&brd[0][2]==brd[1][2]&&brd[1][2]==brd[2][2])
			cout << brd[0][2] << endl;
		else if(brd[0][0]!='+'&&brd[0][0]==brd[1][1]&&brd[1][1]==brd[2][2])
			cout << brd[0][0] << endl;
		else if(brd[0][2]!='+'&&brd[0][2]==brd[1][1]&&brd[1][1]==brd[2][0])
			cout << brd[0][2] << endl;
		else
			cout << "NA" << endl;
	}

	return 0;
}