/* 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 in = new Scanner(System.in);
        double r = in.nextInt();
        double x = in.nextInt();
        double y = in.nextInt();
        double x1 = in.nextInt();
        double y1 = in.nextInt();
        double s1 = Math.abs(x - x1);
        double s2 = Math.abs(y - y1);
        double q = s1*s1 + s2*s2;
        q = Math.sqrt(q);
        double z = (q)/(2*r);
        double t = Math.ceil(z);
        System.out.println((int)t);
	}
}