import java.util.*;
import java.lang.*;
import java.io.*;

public class Codechef
{
    public static void main (String[] args) throws java.lang.Exception
    {
        Scanner sc = new Scanner(System.in);
        
        double r = sc.nextDouble();
        long x1 = sc.nextInt();
        long y1 = sc.nextInt();
        long x2 = sc.nextInt();
        long y2 = sc.nextInt();
        long count = 0;
        long xsq = (x2-x1)*(x2-x1);
        long ysq = (y2-y1)*(y2-y1);
        double d = Math.sqrt(xsq+ysq);
        while(d > 0)
        {
            count++;
            d -= 2*r;
        }
        System.out.println(count);         
    }
}
