import java.util.*;
public class Main {
public static void main(String[] args){
	Scanner scan = new Scanner(System.in);
	double r = scan.nextDouble();
	double x1 = scan.nextDouble();
	double y1 = scan.nextDouble();
	double x2 = scan.nextDouble();
	double y2 = scan.nextDouble();
	double xm=(x1-x2)*(x1-x2);
	double ym=(y1-y2)*(y1-y2);
	double d = Math.sqrt(xm + ym);
	int s=0;
	if(d==0) s=0;
	else if(d<=2*r) s=1;
	else
	{
		while(d>2*r)
		{
			d=d-2*r;
			s++;
		}
		s++;
	}
	System.out.println(s);
}
}

   	 			 	     			  		  	  	 	