#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;
double x[160],y[160],f[160][160],m[160],maxn=999999999;
char s[160];
double jl(int a,int b)
{
	return sqrt((x[a]-x[b])*(x[a]-x[b])+(y[a]-y[b])*(y[a]-y[b]));
}
int main()
{
	freopen("in,txt","r",stdin);
	freopen("out.txt","w",stdout);
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)cin>>x[i]>>y[i];
	for(int i=1;i<=n;i++)
	{
		cin>>s;
		for(int j=1;j<=n;j++)
		if(s[j-1]=='1')
			f[i][j]=jl(i,j);
		else 
			f[i][j]=maxn;
	}
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(i!=j)
				for(int k=1;k<=n;k++)
					if(f[i][k]<maxn-1&&f[k][j]<maxn-1&&i!=k&&j!=k)
						f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(f[i][j]<maxn-100)
				m[i]=max(m[i],f[i][j]);
	double minn=9999999;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
		if(f[i][j]>=maxn-1&&i!=j)
		{
			double t=jl(i,j);
			minn=min(minn,m[i]+m[j]+t);
		}
		for(int i=1;i<=n;i++)
		if(m[i]>minn) minn=m[i];
	printf("%.6lf",minn);
}