백준 7단계 no.2

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        int level = 1;
        int bound = 1;
        while (n > bound) {
            bound += 6 * level;
            level += 1;
        }

        System.out.println(level);

    }
}