#include<cstdio>

#include<iostream>

#include<cstring>

#include<algorithm>

#include<cmath>

#define maxn 255

using namespace std;

char list[maxn][maxn];

double map[maxn][maxn];

int vis[maxn];

int ins[maxn];

int n, m;

struct Node {

	double x;

	double y;

	double len;

}que[maxn];

double get(Node a, Node b) {

	return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y));

}

int dfs(int x, int num) {

	ins[x] = num;

	vis[x] = 1;

	for (int i = 0; i < n; i++) {

		if (!vis[i] && list[x][i] == '1') dfs(i, num);

	}

	return 0;

}

void floyd() {

	for (int k = 0; k < n; k++) {

		for (int i = 0; i < n; i++) {

			for (int j = 0; j < n; j++) {

				map[i][j] = min(map[i][j], map[i][k] + map[k][j]);

			}

		}

	}

}

int main() {

	scanf("%d", &n);

	for (int i =  0; i < n; i++) {

		scanf("%lf %lf", &que[i].x, &que[i].y);

	}

	for (int i = 0; i < n; i++) {

		scanf("%s", list[i]);

	}

	for (int i = 0; i < n; i++) {

		for (int j = 0; j < n; j++) {

			if (list[i][j] == '0') map[i][j] = 1100000.0;

			else map[i][j] = get(que[i], que[j]);

		}

	}

	for (int i = 0; i < n; i++) map[i][i] = 0.0;

	floyd();

	int cnn = 0;

	for (int i = 0; i < n; i++) {

		if (!vis[i]) {

			cnn++;

			dfs(i, cnn);

		}

	}

	for (int i = 0; i < n; i++) {

		que[i].len = 0;

		for (int j = 0; j < n; j++) {

			if (ins[i] == ins[j]) {

				double len = map[i][j];

				que[i].len = max(que[i].len, len);

			}

		}

	}

	double ans = 1100000;

	for (int i = 0; i < n; i++) {

		for (int j = 0; j < n; j++) {

			if (ins[i] != ins[j]) {

				double len = get(que[i], que[j]);

				len += que[i].len + que[j].len;

				ans = min(ans, len);

			}

		}

	}

	for (int i = 0; i < n; i++) {

		ans = max(que[i].len, ans);//特殊情况，原图自己就已经够大的了，没必要再加了

	}

	printf("%.6lf\n", ans);

	return 0;

}