import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	 public static void main(String[] args) {
        int startSum = 1;
        int years = 1;
        int k = 1;
        int currentSum = startSum;

        Scanner scanner = new Scanner(System.in);
        int sum = scanner.nextInt();
        while (currentSum < sum){
            years++;
            k = k*2 + years;
            currentSum += k;
        }
        System.out.println(years);
    }
}