
import java.util.Scanner;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
/**
 *
 * @author KHALED
 */
public class AmrAndPins {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        int r=scan.nextInt();
        int x1=scan.nextInt();
        int y1=scan.nextInt();
        int x2=scan.nextInt();
        int y2=scan.nextInt();
        double xd = x2 - ((double) x1);
        double yd = y2 - ((double) y1);
        double d = Math.sqrt(xd * xd + yd * yd);
        int ans = (int) (d/(r*2));
        if(d/(r*2) - ans >0){
            ans++;
        }
        System.out.println(ans);
    }
}
