import java.io.*;
import java.util.*;
public class Main {  
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader( new InputStreamReader(System.in) );
        Scanner scan= new Scanner(System.in);
        long r,x,y,xx,yy;
        String[] line=br.readLine().split(" ");
        r=Long.parseLong(line[0]);
        x=Long.parseLong(line[1]);
        y=Long.parseLong(line[2]);
        xx=Long.parseLong(line[3]);
        yy=Long.parseLong(line[4]);
        long x1=x-xx;
        long y1=y-yy;
        double distance=Math.sqrt(x1*x1+y1*y1);
        double ans=Math.ceil(distance/(2*r));
        System.out.println(Math.round(ans));
    }   
}
