https://www.e-olymp.com/az/problems/127

/*
    Author: Kanan Asgarli
    https://www.e-olymp.com/az/problems/127
*/
#include <iostream>
#include <algorithm>
using namespace std;
long long s, sum, n, evvelki;
int main()
{
    cin>>s;
    while(sum < s){
        n++;
        evvelki = 2*evvelki + n;
        sum += evvelki;
    }
    cout<<n<<endl;
    return 0;
}