
import java.util.*;

public class Pins {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		long r = sc.nextLong();
		long x1 = sc.nextLong();
		long y1 = sc.nextLong();
		long x2 = sc.nextLong();
		long y2 = sc.nextLong();
		double d = Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
		double res = Math.ceil(d/(2*r));
		System.out.println((long)res);
	}

}
