

import java.math.BigInteger;
import java.lang.String;
import java.util.*;


public class Main {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int r=input.nextInt();
        int x=input.nextInt();
        int y=input.nextInt();
        int x1=input.nextInt();
        int y1=input.nextInt();
        double d=Math.sqrt(Math.pow((x-x1),2)+Math.pow((y-y1),2));
        int ans=(int)Math.ceil(d/r/2);
        System.out.println(ans);

    }
}
