import java.util.*;
public class B507 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
         Scanner s = new Scanner(System.in);
        int r = s.nextInt();
        int x = s.nextInt();
        int y = s.nextInt();
        int x1 = s.nextInt();
        int y1 = s.nextInt();
        double r1 = Math.sqrt(Math.pow(x-x1,2)+Math.pow(y-y1,2));
        r1/=(2*r);
        int res = (int)r1;
        if(res<r1){
            res++;
        }
        System.out.println(res);
	}
}