#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> PII;
#define x first
#define y second

const int N = 200, INF = 0x3f3f3f3f;
char g[N][N];
double dist[N][N];
double maxd[N];
vector<PII> p;

double get_dist(PII a, PII b)
{
    int x = abs(a.x - b.x);
    int y = abs(a.y - b.y);
    return sqrt(x * x + y * y);
}

int main(void)
{
    int n;
    cin >> n;
    for (int i = 0; i < n; i ++)
    {
        int a, b;
        cin >> a >> b;
        p.push_back({a, b});
    }

    for (int i = 0; i < n; i ++)
    {
        for (int j = 0; j < n; j ++)
            cin >> g[i][j];
    }

    for (int i = 0; i < n; i ++)
        for (int j = 0; j < n; j ++)
            if (i == j)
                dist[i][j] = 0;
            else if(g[i][j] == '1')
                dist[i][j] = get_dist(p[i], p[j]);
            else 
                dist[i][j] = INF;

    for (int k = 0; k < n; k ++)
        for (int i = 0; i < n; i ++)
            for (int j = 0; j < n; j ++)
                dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);

    double ans1 = 0, ans2 = INF;
    for (int i = 0; i < n; i ++)
    {
        for (int j = 0; j < n; j ++)
            if (dist[i][j] != INF)
                maxd[i] = max(maxd[i], dist[i][j]);
        ans1 = max(ans1, maxd[i]);
    }

    for (int i = 0; i < n; i ++)
        for (int j = 0; j < n; j ++)
            if (dist[i][j] == INF)
                ans2 = min(ans2, maxd[i] + maxd[j] + get_dist(p[i], p[j]));
    printf("%lf", max(ans1, ans2));

    return 0;
}