#include<cstdio> 
#include<iostream>
#include<cstring>
using namespace std;
int main()
{
	string a[35];
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	    for(int j=1;j<=n;j++)
	    cin>>a[i][j];
	for(int i=1;i<=n;i++)
	    for(int j=1;j<=n;j++)
	{
		if(((a[i-1][j-1]==a[i][j]&&a[i][j]==a[i+1][j+1])||(a[i-1][j]==a[i][j]&&a[i][j]==a[i+1][j])||(a[i-1][j+1]==a[i][j]&&a[i][j]==a[i-1][j-1])||(a[i][j-1]==a[i][j]&&a[i][j]==a[i][j+1]))&&a[i][j]!='.')
		   {
		   	cout<<a[i][j];
		   	return 0;
		   }
	   }
	cout<<"ongoing";
	return 0;   
 }