import java.util.*;
import java.math.*;
import java.math.*;
public class Main {
	static Scanner cin = new Scanner (System.in);
	static double r,x,y,x1,y1;
	public static void main(String[] args) {
		r=cin.nextDouble();
		x=cin.nextDouble();
		y=cin.nextDouble();
		x1=cin.nextDouble();
		y1=cin.nextDouble();
		double l=Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
		int step=(int)(l/(2*r));
		if(step*2*r!=l) step++;
		System.out.println(step);
	}
}