#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<vector>
#include<stack>
#include<cstdlib>
#include<queue>
#include<cstdio>
#include<numeric>
#include<string>
#include<iomanip>
#include<set>
#include<map>
#include<sstream>
#define PII pair<int,int>
#define x first
#define y second
#define PIII pair<int,pair<int,int>>
typedef long long ll;
using namespace std;

const double INF = 1e21;
const int N = 160,M= 3e5;
const ll mod = 1e9 + 7;


int n, m;
double dist[N][N];
double dmax[N];
char g[N][N];
PII a[N];


double get_dist(PII a, PII b)
{
	int dx = a.x - b.x, dy = a.y - b.y;
	return sqrt(dx * dx + dy * dy);
}

void floyd()
{
	for (int k = 0; k < n; k++)
		for (int i = 0; i < n; i++)
			for (int j = 0; j < n; j++)
				dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
}

int main()
{
	cin.tie(0); cout.tie(0)->ios::sync_with_stdio(false);
	cin >> n;
	
	for (int i = 0; i < n; i++)cin >> a[i].x >> a[i].y;

	for (int i = 0; i < n; i++)cin >> g[i];
		
	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++)
			if (i != j)
			{
				if(g[i][j]=='1')dist[i][j] = get_dist(a[i],a[j]);
				else dist[i][j] = INF;
			}


	floyd();

	for (int i = 0; i < n; i++)
		for (int j = 0; j < n; j++)
			if(dist[i][j]<INF)
				dmax[i] = max(dmax[i], dist[i][j]);

	double res1 = 0;
	for (int i = 0; i < n; i++)res1 = max(res1, dmax[i]);

	double res2 = INF;
	for(int i=0;i<n;i++)
		for(int j=0;j<n;j++)
			if (dist[i][j] >= INF)
			{
				res2 = min(res2, get_dist(a[i], a[j]) + dmax[i] + dmax[j]);
			}
	cout << fixed<<setprecision(6)<<max(res1,res2);
	return 0;
}