import java.io.*;
import java.util.*;
public class Main
{
	public static void main(String[] args)throws IOException {
		InputStreamReader read=new InputStreamReader(System.in);
		BufferedReader in=new BufferedReader(read);
		String str=in.readLine();
		String line[]=str.trim().split(" ");
		long r=Long.parseLong(line[0]);
		long x1=Long.parseLong(line[1]);
		long y1=Long.parseLong(line[2]);
		long x2=Long.parseLong(line[3]);
		long y2=Long.parseLong(line[4]);
		long check=2*r;
		double a1=Math.pow((x2-x1),2.0);
		double a2=Math.pow((y2-y1),2.0);
		double d=Math.sqrt(a1+a2);
		System.out.println((int)Math.ceil(d/check));
	}
}
