#include<bits/stdc++.h>
using namespace std;
#define int long long
double a[155][155],ans=INT_MAX,cnt[155],tmp;
int n,x[155],y[155];
signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(i==j)
				a[i][j]=0;
	else
		a[i][j]=INT_MAX;
	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 t;
			cin>>t;
			if(t-'0'==1)
				a[i][j]=sqrt(abs(x[j]-x[i])*abs(x[j]-x[i])+abs(y[j]-y[i])*abs(y[j]-y[i]));
		}
	for(int k=1;k<=n;k++)
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
				if(a[i][k]!=INT_MAX&&a[k][j]!=INT_MAX)
					a[i][j]=min(a[i][j],a[i][k]+a[k][j]);
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++)
			if(a[i][j]!=INT_MAX)
				cnt[i]=max(cnt[i],a[i][j]);
		tmp=max(tmp,cnt[i]);
	}
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(a[i][j]==INT_MAX)
				ans=min(ans,cnt[i]+cnt[j]+sqrt(abs(x[j]-x[i])*abs(x[j]-x[i])+abs(y[j]-y[i])*abs(y[j]-y[i])));
	printf("%.6lf",max(ans,tmp));
	return 0;
}