Vanya got n cubes. He decided to build a pyramid from them. Vanya wants to build the pyramid as follows: the top level of the pyramid must consist of 1 cube, the second level must consist of 1 + 2 = 3 cubes, the third level must have 1 + 2 + 3 = 6 cubes, and so on. Thus, the i-th level of the pyramid must have 1 + 2 + ... + (i - 1) + i cubes.

Vanya wants to know what is the maximum height of the pyramid that he can make using the given cubes.

Input

The first line contains integer n (1 ≤ n ≤ 104) — the number of cubes given to Vanya.

Output

Print the maximum possible height of the pyramid in the single line.

Examples

Input

1


Output

1


Input

25


Output

4

Note

Illustration to the second sample: 

<image>
import java.awt.Point;
import java.io.*;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.*;

import javax.management.IntrospectionException;
import javax.swing.colorchooser.ColorSelectionModel;
import javax.xml.soap.MimeHeader;

import static java.lang.Math.*;
import static java.lang.Math.min;
import java.math.BigDecimal;
import java.math.RoundingMode;

public class Main {

    final boolean ONLINE_JUDGE = System.getProperty("ONLINE_JUDGE") != null;
    BufferedReader in;
    PrintWriter out;
    StringTokenizer tok = new StringTokenizer("");

    void init() throws FileNotFoundException {
        if (ONLINE_JUDGE) {
            in = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
        } else {
            in = new BufferedReader(new FileReader("input.txt"));
            out = new PrintWriter("output.txt");
        }
    }

    String readString() throws IOException {
        while (!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine());
        }
        return tok.nextToken();
    }

    int readInt() throws IOException {
        return Integer.parseInt(readString());
    }

    long readLong() throws IOException {
        return Long.parseLong(readString());
    }

    double readDouble() throws IOException {
        return Double.parseDouble(readString());
    }

    public static void main(String[] args) {
        new Main().run();
        // Sworn to fight and die
    }

    public static void mergeSort(int[] a) {
        mergeSort(a, 0, a.length - 1);
    }

    private static void mergeSort(int[] a, int levtIndex, int rightIndex) {
        final int MAGIC_VALUE = 50;
        if (levtIndex < rightIndex) {
            if (rightIndex - levtIndex <= MAGIC_VALUE) {
                insertionSort(a, levtIndex, rightIndex);
            } else {
                int middleIndex = (levtIndex + rightIndex) / 2;
                mergeSort(a, levtIndex, middleIndex);
                mergeSort(a, middleIndex + 1, rightIndex);
                merge(a, levtIndex, middleIndex, rightIndex);
            }
        }
    }

    private static void merge(int[] a, int levtIndex, int middleIndex,
                              int rightIndex) {
        int length1 = middleIndex - levtIndex + 1;
        int length2 = rightIndex - middleIndex;
        int[] levtArray = new int[length1];
        int[] rightArray = new int[length2];
        System.arraycopy(a, levtIndex, levtArray, 0, length1);
        System.arraycopy(a, middleIndex + 1, rightArray, 0, length2);
        for (int k = levtIndex, i = 0, j = 0; k <= rightIndex; k++) {
            if (i == length1) {
                a[k] = rightArray[j++];
            } else if (j == length2) {
                a[k] = levtArray[i++];
            } else {
                a[k] = levtArray[i] <= rightArray[j] ? levtArray[i++]
                        : rightArray[j++];
            }
        }
    }

    private static void insertionSort(int[] a, int levtIndex, int rightIndex) {
        for (int i = levtIndex + 1; i <= rightIndex; i++) {
            int current = a[i];
            int j = i - 1;
            while (j >= levtIndex && a[j] > current) {
                a[j + 1] = a[j];
                j--;
            }
            a[j + 1] = current;
        }
    }

    public void run() {
        try {
            long t1 = System.currentTimeMillis();
            init();
            solve();
            out.close();
            long t2 = System.currentTimeMillis();
            System.err.println("Time = " + (t2 - t1));
        } catch (Exception e) {
            e.printStackTrace(System.err);
            System.exit(-1);
        }
    }

    class LOL implements Comparable<LOL> {

        int x;
        int y;



        public LOL(int x, int y) {
            this.x = x;
            this.y = y;

        }

        @Override
        public int compareTo(LOL o) {

            return (x - o.x); // ---->
            //return o.x * o.y - x * y; // <----
        }

    }

    class test implements Comparable<test> {

        long x;
        long y;



        public test(long x, long y) {
            this.x = x;
            this.y = y;

        }

        @Override
        public int compareTo(test o) {
            //int compareResult = Long.compare(y, o.y); // ---->

            //if (compareResult != 0) {
            //    return -compareResult;
            //}

            return Long.compare(x, o.x);

            //return o.x * o.y - x * y; // <----
        }

    }

    class data {
        String name;
        String city;

        data(String name, String city) {
            this.city = city;
            this.name = name;
        }
    }

    class record implements Comparable<record> {
        String city;
        Long score;

        public record(String name, Long score) {
            this.city = name;
            this.score = score;
        }

        @Override
        public int compareTo(record o) {
            if (o.city.equals(city)) {
                return 0;
            }

            if (score.equals(o.score)) {
                return 1;
            }

            if (score > o.score) {
                return 666;
            } else {
                return -666;
            }

            //return Long.compare(score, o.score);

        }

    }

    public long gcd(long a, long b) {
        if (a % b == 0)
            return b;
        else
            return gcd(b, a % b);
    }

    boolean prime(int n) {
        for (int i = 2; i <= sqrt(n); i++)
            if (n % i == 0)
                return false;
        return true;
    }

    public int sum(long n) {
        int s = 0;

        while (n > 0) {
            s += (n % 10);
            n /= 10;
        }

        return s;

    }

 /*   public void simulation(int k) {
        long ans = 0;
        int start = 1;
        for (int i = 0; i < k; i++) {
            start *= 10;
        }
        for (int i = start/10; i < start; i++) {
            int locAns = 0;
            for (int j = start/10; j < start; j++) {
                if  (sum(i + j) == sum(i) + sum(j) ) {
                    ans += 1;
                    locAns += 1;
                } else {
                    //.println(i + "!!!" + j);
                }
            }
            //out.println(i + " " + locAns);
        }
        out.println(ans);
    }*/


    public void solve() throws IOException {

        int n = readInt();

        long s = 0;

        int i = 0;

        while (s <= n) {
            i += 1;
            s += (i * (i + 1)) / 2;
        }

        out.print(i - 1);




    }
}