import java.util.*;
import java.lang.*;
import java.io.*;

import java.lang.*;
import java.io.*;
public class main{ 
	 public static void main(String args[])
	 {
		Scanner sc = new Scanner(System.in);
		long r = sc.nextInt();
		long x = sc.nextInt();
		long y = sc.nextInt(),x1 = sc.nextInt(),y1 = sc.nextInt();
		double d = (Math.abs(x1-x)*Math.abs(x1-x))+(Math.abs(y1-y)*Math.abs(y1-y));
		System.out.println((int)Math.ceil(Math.sqrt(d)/(2*r)));
	}
}