#include <bits/stdc++.h>
#define inf 100000000.00
using namespace std;

struct Pos {
	double x, y;
} place[155];
double arrmax[155];

struct edge {
	int y;
	double z;
};

double dist(Pos x, Pos y) {
	return 1.0 * sqrt((x.x - y.x) * (x.x - y.x) + (x.y - y.y) * (x.y - y.y));
}
double dis[155][155];

int main() {
	int n;
	cin >> n;

	for (int i = 1; i <= n; i++) {
		cin >> place[i].x >> place[i].y;
	}

	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			char c;
			cin >> c;

			if (c == '1')
				dis[i][j] = dist(place[i], place[j]);
			else
				dis[i][j] = inf;

		}//初始化成带权无向图
	}

	//接着floyd最短路
	for (int k = 1; k <= n; k++) {
		for (int i = 1; i <= n; i++) {
			for (int j = 1; j <= n; j++) {
				if (i == j)
					continue;

				if (dis[i][k] == inf || dis[k][j] == inf)
					continue;

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

	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			if (i == j || dis[i][j] == inf)
				continue;

			arrmax[i] = max(arrmax[i], dis[i][j]);
		}
	}//每个点能到达的距离最大值

	double minn = 9999999.0;

	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			if (i == j || dis[i][j] != inf)
				continue;
			minn = min(minn, arrmax[i] + arrmax[j] + dist(place[i], place[j]));
		}
	}//任意两个点的连线距离+这两个点能到达距离的最大值 的最小值
	printf("%.6lf", minn);
	return 0;
}