import java.util.*;

public class armspins
{
	public static void main(String args[])
	{
		Scanner sc = new Scanner(System.in);
		long r = sc.nextLong(), x1 = sc.nextLong(), y1 = sc.nextLong(), x2 = sc.nextLong(), y2 = sc.nextLong();
        double a = Math.sqrt(((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1)))/(2*r);
		System.out.print((int)Math.ceil(a));
	}
}