
import java.util.Scanner;

public class Main {

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);
        int r = sc.nextInt();
        int x = sc.nextInt();
        int y = sc.nextInt();
        int a = sc.nextInt();
        int b = sc.nextInt();
        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);
    }
}
