import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner S=new Scanner(System.in);
        Double r=S.nextDouble(),x=S.nextDouble(),y=S.nextDouble(),x1=S.nextDouble(),y1=S.nextDouble(),rez=0d;
        double length=Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));
        while(length>0){
            length-=r*2;
            rez++;
        }
        System.out.println(rez.intValue());
    }

}