import java.lang.Math;
import java.util.Scanner;
public class Demo {

    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int r=sc.nextInt();
        int x0=sc.nextInt();
        int y0=sc.nextInt();
        int x1=sc.nextInt();
        int y1=sc.nextInt();
        int count=0;
        int square=(int)(Math.pow((x0-x1),2)+Math.pow((y0-y1),2));
        int r_2=r*r*4;
        count=(square+r_2-1)/r_2;
        System.out.print(count);
    }
}