import java.util.*;

public class problem287_2 {

	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		int r=in.nextInt();
		int x=in.nextInt();
		int y=in.nextInt();
		int x1=in.nextInt();
		int y1=in.nextInt();
		int dis2=(x-x1)*(x-x1)+(y-y1)*(y-y1);
		int dist=(int)Math.sqrt(dis2);
		if(dist*dist!=dis2)
			++dist;
		int moves=dist/(2*r);
		if(dist%(2*r)!=0)
			moves++;
		System.out.println(""+moves);
	}

}
