import java.util.*;
public class b {
	public static void main(String[] arg)
	{
		new b();
	}
	public b()
	{
		Scanner in = new Scanner(System.in);
		int r = in.nextInt();
		int x = in.nextInt();
		int y = in.nextInt();
		int xp = in.nextInt();
		int yp = in.nextInt();
		double answer = 0;
		int dx = x-xp;
		int dy = y-yp;
		if((dx*dx + dy*dy) % (4*r*r) == 0)
		{
			answer = (dx*dx + dy*dy) / (4*r*r);
			answer = Math.sqrt(answer);
		}
		else
		{
			answer = (dx*dx + dy*dy) / (4*r*r);
			answer = Math.sqrt(answer);
			answer++;
		}
		//answer = Math.sqrt((x-xp)*(x-xp) + (y-yp)*(y-yp)) / (2*r);
		//System.out.println(answer);
		//answer = Math.ceil(answer);
		System.out.println((int)(answer));
		
		in.close();
	}
}
