/**
 * Created by user on 12/15/2014.
 */
import java.util.
        *;
public class three
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        int r = input.nextInt();
        int x = input.nextInt();
        int y = input.nextInt();
        int xp = input.nextInt();
        int yp = input.nextInt();
        System.out.println((int)Math.ceil(Math.sqrt((x-xp)*(x-xp) + (y-yp)*(y-yp))/(2*r)));
    }
}
