import java.util.*;
import java.math.*;

public class Main {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    long r = in.nextLong();
    long x = in.nextLong();
    long y = in.nextLong();
    long xd = in.nextLong();
    long yd = in.nextLong();

    double d = Math.sqrt( (xd-x)*(xd-x) + (yd-y)*(yd-y) );

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