
import java.util.Scanner;

public class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        long r = sc.nextLong();
        long x = sc.nextLong();
        long y = sc.nextLong();
        long a = sc.nextLong();
        long b = sc.nextLong();
        //System.out.println("sq: "+(x-a)*(x-a)+(y-b)*(y-b));
        double distance = Math.sqrt(((x-a)*(x-a))+((y-b)*(y-b)));
        //System.out.println("dis: "+distance);
        double m = distance/((double)r*2.0);
        //System.out.println("m: "+m);
        //if(distance==0.0) System.out.println("0");
        if(m!=(int)m) m++;
        System.out.println((int)m);
    }
}
