#include<bits/stdc++.h>
#pragma GCC optmeize(3)
using namespace std;
double x[10000],z,y[10000],f[10000][10000],m[151]={0},minn=1e14;
int main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)cin>>x[i]>>y[i];
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++){
			char si;
			cin>>si;
			if(si=='1')f[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
			else f[i][j]=1e17;
		}
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			for(int k=1;k<=n;k++)
				if(f[i][k]<1e10-1&&f[k][j]<1e10-1&&f[i][k]+f[k][j]<f[i][j])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]<1e10-1&&m[i]<f[i][j])m[i]=f[i][j];
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(i!=j&&f[i][j]>1e10-1){
				z=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
				minn=min(minn,m[i]+m[j]+z);
			}
	for(int i=1;i<=n;i++)minn=max(minn,m[i]);
	printf("%.6lf\n",minn);
	return 0;
  }