/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Codechef
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
		Scanner s=new Scanner(System.in);
		int r=s.nextInt();
		int x1=s.nextInt();
		int y1=s.nextInt();
		int x2=s.nextInt();
		int y2=s.nextInt();
		int ans=0;
		double dist=Math.sqrt((x2-x1)*(x2-x1)+ (y2-y1)*(y2-y1));
		dist=dist/(2*r*1.0);
		if(dist%1==0)
		ans=(int)dist;
		else
		ans=(int)dist+1;
		System.out.println(ans);
	}
}
