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);
		int r = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();int x1 = sc.nextInt();int y1 = sc.nextInt();
		double d = ((x1-x)*(x1-x))+((y1-y)*(y1-y));
		System.out.println((int)Math.ceil(Math.sqrt(d)/(2*r)));
	}
}