/* package whatever; // 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 Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner obj = new Scanner(System.in);
		
		int r = obj.nextInt();
		int x = obj.nextInt();
		int y = obj.nextInt();
		int x1 = obj.nextInt();
		int y1 = obj.nextInt();
		
		double dist = Math.pow( (Math.pow((x-x1),2) + Math.pow((y-y1),2) ) ,0.5);
		
		int d = (int) dist;
		
		double diff = dist - d;
		
		if(dist==0)
		{
			System.out.println("0");
		}
		else
		{
			int steps = d/(2*r);
			
			if(diff==0 && dist%2==0)
			{
				System.out.println(steps);	
			}
			else
			{
				System.out.println(++steps);
			}
			
		}
		
	}
}