import java.util.*;


public class bucky{


public static void main (String args[]) {

Scanner input=new Scanner(System.in);

HashMap<Integer, Integer> map= new HashMap<Integer, Integer>();


	long r=input.nextInt();

	    
	    long x1=input.nextInt();
	    long y1=input.nextInt();
	  
	     long x2=input.nextInt();
	    long y2=input.nextInt();
	    
	 
	  double result=Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
	    
	   if(result%(2*r)==0) result=result/(2*r);
	   else result=1+result/(2*r);
	    
	    
	    
    System.out.println((int)result);
	

 


    
    
}


}