import java.util.Scanner;

public class Main{
	public static void main(String[] args) {
		Scanner scn = new Scanner(System.in);
		double redius = scn.nextDouble();//taking redius
		double cX = scn.nextDouble(),cY = scn.nextDouble();//taking Center
		double x = scn.nextDouble(),y = scn.nextDouble();//taking disare point
		
		//System.out.println(getDistance(cX,cY,x,y));
		int minmunStep = (int)Math.ceil((getDistance(cX,cY,x,y)/(redius*2)));
		
		
		System.out.println(minmunStep);
		scn.close();
	}
	
	public static double getDistance(double x1,double y1,double x2,double y2) {
		double dx = x2 - x1;
		double dy = y2 - y1;
		
		double distance = Math.sqrt(dx*dx + dy*dy);
		
		return distance;
	}
}	

    			 		      	 	  	    		  	