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

public class Main {
  public static void main(String[] args) {
    final double EPS = 1e-10;
    Scanner in = new Scanner(System.in);
    double r = in.nextDouble();
    Point from = new Point();
    from.x = in.nextDouble();
    from.y = in.nextDouble();
    Point to = new Point();
    to.x = in.nextDouble();
    to.y = in.nextDouble();
    double dist = from.distanceFrom(to);
    System.out.println((long) Math.ceil(dist / (2 * r)));
  }

  static class Point {
    public double x;
    public double y;

    public double distanceFrom(Point other) {
      return Math.sqrt(Math.pow(this.x - other.x, 2) + Math.pow(this.y - other.y, 2));
    }
  }
}