/* 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 sc = new Scanner(System.in);
		long n = sc.nextLong();
		n *= 2;
		long x1 = sc.nextLong();
		long y1 = sc.nextLong();
		long x2 = sc.nextLong();
		long y2 = sc.nextLong();
		
		double d = Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
		d = d/n;
		int a = (int)Math.ceil(d);
		System.out.println(a);
	}
}