import java.awt.geom.Point2D;
import java.util.Scanner;

public class B507 {
    public static Scanner input=new Scanner(System.in);
    public static void main(String[] args) {
        int rad=input.nextInt();
        int nowX=input.nextInt();
        int nowY=input.nextInt();
        int reqX=input.nextInt();
        int reqY=input.nextInt();
        double distance= Point2D.distance(nowX,nowY,reqX,reqY);
        double i;
        for(i=0;i<10000000;i++)
        {
            if((i*rad)>=distance/2)
                break;
        }
        System.out.println((int)i);
    }
}