import java.util.*;
public class Main
{
	public static void main(String[] args)
	{
	    Scanner sc=new Scanner(System.in);
		long r=sc.nextInt()*2;
		long x1=sc.nextInt();
		long y1=sc.nextInt();
		long x2=sc.nextInt();
		long y2=sc.nextInt();
		long ans=(long)(Math.pow((x2-x1),2) + Math.pow((y2-y1),2));
		long count=0;
		if(Math.sqrt(ans)%r!=0)
		count++;
		count+=(Math.sqrt(ans)/r);
		System.out.println(count);
	}
}
