import java.util.Scanner;
import java.lang.Math;

public class Amr{
    public static void main(String args[]){
        Scanner scan = new Scanner(System.in);
        
        int r = scan.nextInt();
        int x1 = scan.nextInt();
        int y1 = scan.nextInt();
        
        int x2 = scan.nextInt();
        int y2 = scan.nextInt();
        
        
        double distance = Math.sqrt(Math.pow(x2-x1,2) + Math.pow(y2-y1,2));
        
        int moves = (int)(distance / (2*r)) + (distance%(2*r) == 0 ? 0 : 1);
        
        System.out.println(moves);
    }
}