#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <cctype>
#include <sstream>
#include <string>
#include <list>
#include <vector>
#include <queue>
#include <set>
#include <stack>
#include <map>
#include <utility>
#include <numeric>
#include <algorithm>
#include <iterator>
#include <bitset>
#include <complex>
#include <fstream>
using namespace std;
typedef long long ll;
const double EPS = 1e-9;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define MSG(a) cout << #a << " " << a << endl;
#define REP(i, x, n) for(int i = x; i < n; i++)
template<class T> T RoundOff(T a){ return int(a+.5-(a<0)); }
template<class T, class C> void chmax(T& a, C b){ if(a < b) a = b; }
template<class T, class C> void chmin(T& a, C b){ if(b < a) a = b; }
template<class T, class C> pair<T, C> mp(T a, C b){ return make_pair(a, b); }


bool line(vector<string> v, int len)
{
	int n = v.size();
	int x = len - 1, y = 0;
	
	// ツ右ツ湘」ツつゥツづァツ湘」ツ板シツ閉ェ
	rep(i, len)
	{
		if(v[y][x] == '0') break;
		else if(i + 1 == len) return true;
		x--;
		y++;
	}
	
	// ツ右ツ湘」ツつゥツづァツ可コツ板シツ閉ェ
	x = n - 1;
	y = n - len;
	rep(i, len)
	{
		if(v[y][x] == '0') break;
		else if(i + 1 == len) return true;
		x--;
		y++;
	}
	
	// ツ債カツ湘」ツつゥツづァツ湘」ツ板シツ閉ェ
	x = n - len;
	y = 0;
	rep(i, len)
	{
		if(v[y][x] == '0') break;
		else if(i + 1 == len) return true;
		x++;
		y++;
	}
	
	// ツ債カツ湘」ツつゥツづァツ可コツ板シツ閉ェ
	x = 0;
	y = n - len;
	rep(i, len)
	{
		if(v[y][x] == '0') break;
		else if(i + 1 == len) return true;
		x++;
		y++;
	}
	
	return false;	
}
int main()
{
    int n;
	while(cin >> n && n)
	{
		vector<string> v(n);
		rep(i, n) cin >> v[i];
		
		rep(i, n)
		{
			if(count(ALL(v[i]), '0') == 0)
			{
				cout << n << endl;
				goto ng;
			}
			
			rep(j, n)
			{
				if(v[j][i] == '0') break;
				else if(j + 1 == n)
				{
					cout << n << endl;
					goto ng;
				}
			}
		}
		
		for(int i = n; 0 < i; i--) if(line(v, i)) 
		{
			cout << i << endl;
			goto ng;
		}
		
		cout  << 0 << endl;
			
		ng:;
	}
}