import java.util.Scanner;

/**
 * Created by vignesh on 7/6/2017.
 */
public class amrandpins {
    public static void main(String[] args) {
        Scanner in  = new Scanner(System.in);
        int r = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        double dist = Math.sqrt(Math.pow(x-x1, 2) + Math.pow(y-y1, 2));
        int rot  =(int) Math.ceil(dist/(2*r));
        System.out.print(rot);
    }
}
