import java.util.Scanner;
import static java.lang.Math.*;
public class Main {

    public static void main(String[] args) {
        Scanner scan = new Scanner (System.in);
        long r = scan.nextInt()*2;
        long x = scan.nextInt();
        long y = scan.nextInt();
        long x1 = scan.nextInt();
        long y1 = scan.nextInt();
        long dlin= (long) ceil(sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1)));
        //System.out.println(dlin);
        if (dlin%r!=0) System.out.println(dlin/r+1);
        else System.out.println(dlin/r);
    }
}