#include <cstdio>

#include <cstring>

#include <algorithm>

#include <cmath>

#include <vector>

#include <cassert>

using namespace std;

const int MAX_NODE = 200;

const double INF = 200000;

double Dist[MAX_NODE][MAX_NODE];

int TotNode, TotBlock;

struct Coor//Coordinate

{

    int X, Y;

    double Dist(const Coor& a)const

    {

        double x1 = X, y1 = Y, x2 = a.X, y2 = a.Y;

        double dx = abs(x1 - x2), dy = abs(y1 - y2);

        return sqrt(dx * dx + dy * dy);

    }

};

struct Node

{

    Coor Coordinate;

    double MaxDist;

}_nodes[MAX_NODE];

void InitDist()

{

    for (int i = 0; i < MAX_NODE; i++)

        for (int j = 0; j < MAX_NODE; j++)

            Dist[i][j] = INF;

    for (int i = 0; i < MAX_NODE; i++)

        Dist[i][i] = 0;

}

void Read()

{

    scanf("%d", &TotNode);

    for (int i = 1; i <= TotNode; i++)

        scanf("%d%d\n", &_nodes[i].Coordinate.X, &_nodes[i].Coordinate.Y);

    char s[MAX_NODE];

    for (int i = 1; i <= TotNode; i++)

    {

        scanf("%s", s + 1);

        for (int j = 1; j <= TotNode; j++)

            if (s[j] - '0')

                Dist[i][j] = _nodes[i].Coordinate.Dist(_nodes[j].Coordinate);

    }

}

void Floyd()

{

    for (int k = 1; k <= TotNode; k++)

        for (int i = 1; i <= TotNode; i++)

            for (int j = 1; j <= TotNode; j++)

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

}

double MaxMaxDist;

void GetNodeMaxDist()

{

    for (int i = 1; i <= TotNode; i++)

        for (int j = 1; j <= TotNode; j++)

            if (Dist[i][j] < INF)

            {

                _nodes[i].MaxDist = max(_nodes[i].MaxDist, Dist[i][j]);

                MaxMaxDist = max(MaxMaxDist, _nodes[i].MaxDist);

            }

}

double GetAns()

{

    double ans = INF;

    for (int i = 1; i <= TotNode; i++)

        for (int j = 1; j <= TotNode; j++)

            if (Dist[i][j] == INF)

                ans = min(ans, _nodes[i].MaxDist + _nodes[j].MaxDist + _nodes[i].Coordinate.Dist(_nodes[j].Coordinate));

    return max(ans, MaxMaxDist);

}

int main()

{

    InitDist();

    Read();

    Floyd();

    GetNodeMaxDist();

    printf("%.6f\n", GetAns());

    return 0;

}