백준 2292

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main2292 {

	public static void main(String[] args) throws IOException {
		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.parseInt(bf.readLine());
		int cnt = 1;
		int range = 2;

		if (N == 1) {
			System.out.println(1);
		} else {
			while (range <= N) {
				range = range + (6 * cnt);
				cnt++;
			}
			System.out.println(cnt);
		}

	}

}