https://www.luogu.org/problemnew/show/P1522

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,q;
int ans,cnt,flag,temp,sum;
int a[N];
char str;
struct node{
    int x,y;
}p[N];
double mp[N][N];
double dis[N];
double dist(int i,int j){
    return sqrt((p[i].x-p[j].x)*(p[i].x-p[j].x)+(p[i].y-p[j].y)*(p[i].y-p[j].y));
}
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d%d",&p[i].x,&p[i].y);
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            scanf("%1d",&k);
            if(k){
                mp[i][j]=dist(i,j);
            }else if(i!=j){
                mp[i][j]=INF;
            }
        }
    }
    for(int k=1;k<=n;k++)
        for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
                    mp[i][j]=min(mp[i][j],mp[i][k]+mp[k][j]);//首先Floyd求一遍最短路径，标准五行代码
    double l1=0;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++){
            if(mp[i][j]!=INF)dis[i]=max(mp[i][j],dis[i]);//这个事求每一个点距离它最远的点的距离
            l1=max(l1,dis[i]);//这个是牧区目前的最大直径
        }
    double l2=INF;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=n;j++)
            if(mp[i][j]==INF)
                l2=min(l2,dis[i]+dist(i,j)+dis[j]);//这个是牧区目前的最大直径
     printf("%.6f\n",max(l1,l2));
    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}