

 import java.util.*;
 
public class BruteForce{
    public static Scanner in=new Scanner(System.in);
  
    
    public static double getDist(int x1,int y1,int x2,int y2){
        double dist=Math.sqrt((Math.pow(Math.abs(x1-x2),2))+(Math.pow(Math.abs(y1-y2),2)));
        return dist;
    }
    public static void main(String[]args){
        int r=in.nextInt();
        int x1=in.nextInt();
        int y1=in.nextInt();
        int x2=in.nextInt();
        int y2=in.nextInt();
        
        double dist=getDist(x1,y1,x2,y2);
        dist-=r;
        if(dist<=0)
            System.out.println("0");
        else{
            long ans=(long) (dist/r);
            System.out.println(ans);
        }
    }
}