#include<bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353;
using namespace std;
using ll=long long;
using ul=unsigned long long;
int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1};
int dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};
using Graph=vector<vector<int>>;
int main(){
    ll n;
    cin>>n;
    cout<<(int)(sqrt(n/3))<<endl;
}