#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=155;
double dist[N][N];
int a[N][N];
int x[N],y[N];
int fa[N];
int find(int x)
{
	if(fa[x]==x) return x;
	return fa[x]=find(fa[x]);
}
void merge(int x,int y)
{
	int f1=find(x),f2=find(y);
	if(f1!=f2) fa[x]=y;
}
double add[N],maxx[N];
double d(int xx,int yy)
{
	return sqrt((x[xx]-x[yy])*(x[xx]-x[yy])+(y[xx]-y[yy])*(y[xx]-y[yy]));
}
signed main()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>x[i]>>y[i];
	}
	for(int i=1;i<=n;i++)
	{
		fa[i]=i;
	}
	for(int i=1;i<=n;i++)
	{
		string s;
		cin>>s;
		for(int j=0;j<s.size();j++)
		{
			if(s[j]=='1')
			{
				a[i][j+1]=1;
			}
		}
	}
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(i==j) dist[i][j]=0;
			else if(a[i][j])
			{
				dist[i][j]=d(i,j);
				merge(i,j);
			}
			else dist[i][j]=0x3f3f3f3f;
		}
	}
	for(int k=1;k<=n;k++)
	{
		for(int i=1;i<=n;i++)
		{
			for(int j=1;j<=n;j++)
			{
				dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j]); 
			}
		}
	}
	double ans=0x3f3f3f3f;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(find(i)==find(j))
			{
				maxx[i]=max(maxx[i],dist[i][j]);
			}
			add[find(i)]=max(add[find(i)],maxx[i]);
		}
	}
	for(int i=1;i<=n;i++)
	{
		for(int j=i+1;j<=n;j++)
		{
			if(find(i)!=find(j))
			{
				ans=min(ans,(double)max(maxx[i]+maxx[j]+d(i,j),max(add[find(i)],add[find(j)])));
			}
		} 
	}
	printf("%.6lf",ans);
	
	return 0;
}