import java.util.Scanner;
import java.util.Arrays;
import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.FileInputStream;

public class Test{

	public static void main(String[] args){

		try{

			//Scanner in = new Scanner(new FileInputStream("test.txt"));

			Scanner in = new Scanner(System.in);
	
			int r,x,y,x1,y1;
			double d,rep;

			r = in.nextInt();
			x = in.nextInt();
			y = in.nextInt();
			x1 = in.nextInt();
			y1 = in.nextInt();

			d = Math.sqrt(Math.pow(x-x1,2)+Math.pow(y-y1,2));

			if((d % (2*r)) == 0){

				rep = d/(2*r);
	
			}else{
				rep = d/Math.sqrt(2*Math.pow(r,2));
				rep = Math.ceil(rep);
			}

			rep = (int)rep;
			System.out.printf("%.0f\n", rep);
		}catch(Exception e){

			e.printStackTrace();

		}

	}
}