/*********************************************************************
    程序名:
    版权:
    作者:
    日期: 2022-06-13 13:16
    说明:
*********************************************************************/
#include <bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define rep(i,x,n) for(register int i=x;i<n;i++)
#define repd(i,x,n) for(register int i=x;i<=n;i++)
#define MAX 1000005
#define MOD 1000000007
#define FI first
#define SE second
#define MP make_pair
#define PB push_back
#define PII pair<int,int>

template<class T>inline void rd(T &x) {
	x = 0;
	char o, f = 1;
	while (o = getchar(), o < 48)
		if (o == 45)
			f = -f;
	do
		x = (x << 3) + (x << 1) + (o ^ 48);
	while (o = getchar(), o > 47);
	x *= f;
}

template<class T>inline void print(T x, bool op = 1) {
	static int top, stk[105];
	if (x < 0)
		x = -x, putchar('-');
	if (x == 0)
		putchar('0');
	while (x)
		stk[++top] = x % 10, x /= 10;
	while (top)
		putchar(stk[top--] + '0');
	putchar(op ? '\n' : ' ');
}
using namespace std;

const int N = 200;
const double INF = 2e16;
int n, m, k;
double dis[N][N];
int g[N][N];

struct node {
	double x, y;
} ns[N];
int f[N];

int inline find(int x) {
	if (f[x] == x)
		return x;
	return f[x] = find(f[x]);
}

double cal(node a, node b) {
	return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}

void floyed() {
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			for (int k = 1; k <= n; k++)
				dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
}

map<int, int > id;
int cnt = 0, bel[N];
vector<int > blo[N];

void dsu() {
	for (int i = 1; i <= n; i++)
		for (int j = i + 1; j <= n; j++)
			if (g[i][j]) {
				int fx = find(i), fy = find(j);
				f[fx] = fy;
			}

	for (int i = 1; i <= n; i++) {
		int fx = find(f[i]);
		if (!id[fx])
			id[fx] = ++cnt;
		blo[id[fx]].PB(i);
		bel[i] = id[fx];
	}
}
double ans_blo[N], ans_dot[N];

void dot_mx() {
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			if (dis[i][j] != INF)
				ans_dot[i] = max(ans_dot[i], dis[i][j]);
}
double final_ans = 2e16;

void blo_mx() {
	for (int i = 1; i <= cnt; i++) {
		for (int j = 0; j < blo[i].size(); j++) {
			ans_blo[i] = max(ans_blo[i], ans_dot[blo[i][j]]);
			//final_ans = max(final_ans, ans_blo[i]);
		}
	}
}


void two_links() {
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			if (dis[i][j] == INF)
				final_ans = min(final_ans, max(
			{ans_blo[bel[i]], ans_blo[bel[j]], ans_dot[i] + ans_dot[j] + cal(ns[i], ns[j])} ));
		}
	}
}

void solve() {
	cin >> n;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= n; j++)
			dis[i][j] = INF;
	for (int i = 1; i <= n; i++)
		dis[i][i] = 0;
	for (int i = 1; i <= n; i++)
		cin >> ns[i].x >> ns[i].y;
	for (int i = 1; i <= n; i++) {
		string s;
		cin >> s;
		for (int j = 0; j < s.length(); j++) {
			g[i][j + 1] = s[j] - '0';
			if (g[i][j + 1])
				dis[i][j + 1] = dis[j + 1][i] = cal(ns[i], ns[j + 1]);
		}
	}
	floyed();
	dsu();
	dot_mx();
	blo_mx() ;
	two_links();
	cout << fixed << setprecision(6) << final_ans;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
//	int T;
//	cin>>T;
//	while(T--)
	solve();
	return 0;
}