#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0, i##_len = (n); i < i##_len; ++i)
#define rep2(i, x, n) for(int i = x, i##_len = (n); i < i##_len; ++i)
#define all(n) begin(n), end(n)
using ll = long long;
using P = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vs = vector<string>;
using vc = vector<char>;
using vb = vector<bool>;
using vd = vector<double>;
vi dir = {-1, 0, 1, 0, -1, -1, 1, 1, -1};

int main() {
  ll n;
  cin >> n;
  cout << n / 3 << endl;
}
#include <stdio.h>

int
main(void)
{
	char line[80];
	int x;

	if (gets(line)) {
		if (sscanf(line, "%d", &x) == 1) {
			printf("%d\n", x*x*x);
		}
	}

	return 0;
}