import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long n = scan.nextLong();
		scan.close();
		long ans = (long)Math.sqrt((double)n / 3);
		if(ans == 0) {
			System.out.println(1);
		}else {
			System.out.println(ans);
		}
	}
}