import java.util.*;

public class Dragons {

	public static void main(String[] args) {
	       Scanner sc=new Scanner(System.in);
               long r=sc.nextLong();
               long x1=sc.nextLong();
               long y1=sc.nextLong();
               long x2=sc.nextLong();
               long y2=sc.nextLong();
               long ds=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
               double d=Math.sqrt(ds);
               System.out.print((int)Math.ceil(d/(2*r)));
               
               
}
}