import java.util.Scanner;
public class Main507B
{
  public static void main(String[] args)
  {
    Scanner sc=new Scanner(System.in);
    int r=sc.nextInt();
    int x=sc.nextInt();
    int y=sc.nextInt();
    int x2=sc.nextInt();
    int y2=sc.nextInt();
    int diff_x=Math.abs(x-x2);
    int diff_y=Math.abs(y-y2);
    if(diff_x==0&&diff_y==0)
      System.out.println(0);
    else
    {
      double dist=Math.sqrt(diff_x*diff_x+diff_y*diff_y);
      dist=dist/(2*r);
      double ans=Math.ceil(dist);
      System.out.println((int)ans);
    }
  }
}
      
      
      