#include <iostream>
#include <cmath>
#include <vector>
#include <cstring>
#include <queue>
#include <climits>
using namespace std;
const int MAXN = 153;
double e[MAXN][MAXN],dis[MAXN][MAXN],len[MAXN];
pair<int,int> cor[MAXN];
int n,cnt;
int far[MAXN];
bool vis[MAXN],in[MAXN];
void Dijkstra(int s){	
	priority_queue<pair<double,int> > q;
	memset(vis,0,sizeof(vis));
	q.push(make_pair(0,s));
	dis[s][s] = 0;
	if(!in[s]) cnt++;
	while(q.size()){
		int x = q.top().second;
		q.pop();
		if(!in[x]) far[x] = cnt,in[x] = 1;
		if(vis[x]) continue;
		vis[x] = 1;
		for(int i = 1; i <= n; i++){
			if(i != x && e[x][i] != 0){
				
				if(dis[s][i] > dis[s][x] + e[x][i]){
					dis[s][i] = dis[s][x] + e[x][i];
					dis[s][0] = max(dis[s][i],dis[s][0]);
					if(!vis[i]) q.push(make_pair(-e[s][i],i));
				}
			}	
		}
	}
}
double cal(int i,int j){
	return sqrt((cor[i].first - cor[j].first) * (cor[i].first - cor[j].first) + (cor[i].second - cor[j].second) * (cor[i].second - cor[j].second));
}
int main(){
	cin >> n;
	double ans = 2147483647;
	for(int i = 1; i <= n; i++) {
		int x,y;
		cin >> x >> y;
		cor[i] = make_pair(x,y);
	}
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= n; j++){
			scanf("%1d",&e[i][j]);
			if(e[i][j]) e[i][j] = cal(i,j);
		}
	}
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			dis[i][j] = 2147483647;
	for(int i = 1; i <= n; i++) dis[i][0] = 0;
	for(int i = 1; i <= n; i++) Dijkstra(i);

	for(int i = 1;i <= n; i++)
		len[far[i]] = max(len[far[i]],dis[i][0]);
	
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= n; j++){
			if(far[i] != far[j]){
				double l = cal(i,j);
				double g = max(l + dis[i][0] + dis[j][0],max(len[far[i]],len[far[j]]));
				ans = min(ans,g);
			}
		}
	}
	printf("%6f",ans);
	return 0;
}