Solution

#include <bits/stdc++.h>

using namespace std;
double dis[200][200], mdis[200];
int x[200], y[200];
int main() {
	int n,m;
	cin >> n;
	for (int i = 1; i <= n; ++i) cin >> x[i] >> y[i]; 
	
	for (int i = 1; i <= n; ++i)
		for (int j = 1; j <= n; ++j) {
			dis[i][j] = INT_MAX / 3;
			
	}
	
	for (int u = 1; u <= n; ++u) {
		for (int v = 1; v <= n; ++v) {
			char c;
			cin >> c;
			if (c == '1')
				dis[u][v] = sqrt((x[u] - x[v]) * (x[u] - x[v]) + (y[u] - y[v]) * (y[u] - y[v]));
		}
	}
	for (int k = 1; k <= n; ++k) 
		for (int i = 1; i <= n; ++i)
			for (int j = 1; j <= n; ++j)
				if (dis[i][j]  > dis[i][k] + dis[k][j])
				dis[i][j] = dis[i][k] + dis[k][j];
	double ans = 0;
	
	for (int i = 1; i <= n; ++i)
		for (int j = 1; j <= n; ++j) {
			if (dis[i][j] != INT_MAX / 3 && i != j) {
				ans = max(ans, dis[i][j]);
				mdis[i] = max(mdis[i], dis[i][j]);
			}
		}
	
	double d = DBL_MAX;	
	for (int i = 1; i <= n; ++i)
		for (int j = i + 1; j <= n; ++j)
			if (dis[i][j] == INT_MAX / 3 && i != j)
				d = min(d, mdis[i] + mdis[j] + 
				sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j])) ); 
			
	

	cout << fixed << setprecision(6) << max(ans, d) << endl;
	return 0;
}