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