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

public class codeforcesB {

    
    public static void main(String[] args) {
        
        
        Scanner sc = new Scanner(System.in);
        int r = sc.nextInt()*2;
        int x1 = sc.nextInt();
        int y1 = sc.nextInt();
        int x2 = sc.nextInt();
        int y2 = sc.nextInt();
        
        long x = Math.abs(x2-x1);
        long y = Math.abs(y2-y1);
        
        double d  =  Math.sqrt(x*x + y*y);
        
        System.out.println((int)Math.ceil(d/r));
    }
}
