
import java.awt.Point;
import java.util.Scanner;


public class Main {
   
    public static void main(String [] args){
        Scanner sc=new Scanner(System.in);
        int r=sc.nextInt();
        Point oldCenter=new Point(sc.nextInt(),sc.nextInt());
        Point newCenter=new Point(sc.nextInt(),sc.nextInt());
        double diff=(oldCenter.x-newCenter.x)*(oldCenter.x-newCenter.x)+(oldCenter.y-newCenter.y)*(oldCenter.y-newCenter.y);
        diff=Math.sqrt(diff);
        
        System.out.println((int)Math.ceil(diff/(2*r)));
    }
}
