import java.io.IOException;
import java.util.Scanner;

public class B {

	static int r;
	static int x0;
	static int y0;
	static int a;
	static int b;

	public static void main(String[] args) throws NumberFormatException,
			IOException {
		Scanner sc = new Scanner(System.in);
		r = sc.nextInt();
		x0 = sc.nextInt();
		y0 = sc.nextInt();
		a = sc.nextInt();
		b = sc.nextInt();
		double dx = a - x0;
		double dy = b - y0;
		double dst = Math.sqrt((dx * dx * 1.0) + (dy * dy * 1.0));
		int cnt =0 ;
		while(dst>0){
			dst-=(2*r);
			cnt++;
		}
		System.out.println(cnt);
		
	}

}