#include <bits/stdc++.h>
using namespace std;
int n,x[155],y[155];
double f[155][155],dis[155],r1,r2=10000000;
char a;
int main (){
	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++){
			f[i][j]=10000000;
		}
	}
	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++){
			cin>>a;
			if (a=='1'){
				f[i][j]=f[j][i]=sqrt((double)(x[i]-x[j])*(x[i]-x[j])+(double)(y[i]-y[j])*(y[i]-y[j]));
			}
		}
	}
	for (int k=1;k<=n;k++){
		for (int i=1;i<=n;i++){
			if (i!=k){
				for (int j=1;j<=n;j++){
					if (i!=j&&j!=k&&f[i][k]+f[k][j]<f[i][j]){
						f[i][j]=f[j][i]=f[i][k]+f[k][j];
					}
				}
			}
		}
	}
	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++){
			if (i!=j&&f[i][j]!=10000000&&f[i][j]>dis[i]){
				dis[i]=f[i][j];
				r1=max(dis[i],r1);
			}
		}
	}
	for (int i=1;i<=n;i++){
		for (int j=1;j<=n;j++){
			if (i!=j&&f[i][j]==10000000){
				r2=min(r2,dis[i]+dis[j]+sqrt((double)(x[i]-x[j])*(x[i]-x[j])+(double)(y[i]-y[j])*(y[i]-y[j])));
			}
		}
	}
	printf ("%.6lf",max(r1,r2));
	return 0;
}