#include <bits/stdc++.h>   using namespace std;   const int inf = (int)1e9;   const int mod = (int)1e9 + 7;   const double pi = acos(-1.0);   const double eps = 1e-9;   const int maxn = (int)2e6 + 11;   long long n;   long long a[maxn];   long long sum[maxn];   int main() {     cin >> n;     a[1] = 2;     sum[1] = 2;     for (int i = 2; i <= 2000000; i++) {       a[i] = a[i - 1] + 3;       sum[i] = sum[i - 1] + a[i];     }     int ans = 0;     for (int i = 1; sum[i] <= n; i++) {       if ((n - sum[i]) % 3 == 0) ans++;     }     cout << ans << endl;     return 0;   }   