#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using ld = long double;
const ll mod = 998244353;
const ll INF = (1LL << 60);

int main() {
    int N;
    cin >> N;
    ld V = ld(N) * ld(N) * ld(N) * ld(2.18169499062491237350);
    cout << setprecision(450) << V << endl;
    return 0;
}