import java.util.Scanner;

public class B507 {

    public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    
    int r=sc.nextInt();
    int x1=sc.nextInt();
    int y1=sc.nextInt();
    int x2=sc.nextInt();
    int y2=sc.nextInt();
    
     double distance=Math.sqrt(Math.abs(x2-x1)*Math.abs(x2-x1)+Math.abs(y2-y1)*Math.abs(y2-y1));
     int d=2*r;
     if(distance%d==0)
     System.out.println((int)distance/d);
     else System.out.println((int)distance/d+1);
    
    }
}