import java.util.Scanner;

public class P507B {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    int r = input.nextInt();
    int x1 = input.nextInt();
    int y1 = input.nextInt();
    int x2 = input.nextInt();
    int y2 = input.nextInt();

    int dx = x2 - x1;
    int dy = y2 - y1;

    double d = Math.sqrt((long)dx * dx + (long)dy * dy);

    System.out.println((int)Math.ceil(d / (2 * r)));

  }
}
