#include <cstdio>
#include <cstdint>
#include <cmath>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <queue>
#include <algorithm>
#include <numeric>
#include <cassert>
using namespace std;
namespace atcoder{};using namespace atcoder;

using ull = uint64_t;
using ll = int64_t;
using vi = vector<int>;
using vll = vector<ll>;
using vs = vector<string>;
using ld = long double;
using P = pair<ll,ll>;
using G = vector<vector<int>>;

#ifdef MYDEBUG
#define LO(...) fprintf(stderr, __VA_ARGS__)
#define debug(x) cerr << "\033[33m(line:" << __LINE__ << ") " << #x << ": " << x << "\033[m" << endl
#else
#define LO(...) (void)0
#define debug(x) (void)0
#endif

#define reps(i,a,n) for(ll i##_len = (ll)(n), i = (a); i < i##_len; ++i)
#define rep(i,n) reps(i,0,n)
#define rrep(i,n) reps(i,1,n+1)
#define repd(i,n) for(ll i=n-1;i>=0;i--)
#define rrepd(i,n) for(ll i=n;i>=1;i--)

#define inp(i) ll i; cin >> i;
#define inps(s) string s; cin >> s;
#define inpp(p) cin >> (p).first >> (p).second;
#define inpv(v,N) vll v(N);rep(i,N)cin>>v[i];
#define inpg(g,N,M) g.resize(N);rep(i,M){inp(a);inp(b);a--,b--;g[a].push_back(b);g[b].push_back(a);}
#define all(v) begin(v),end(v)
#define YESNO(bool) if(bool){cout<<"YES"<<endl;}else{cout<<"NO"<<endl;}
#define yesno(bool) if(bool){cout<<"yes"<<endl;}else{cout<<"no"<<endl;}
#define YesNo(bool) if(bool){cout<<"Yes"<<endl;}else{cout<<"No"<<endl;}
#define YES cout<<"YES"<<endl
#define NO cout<<"NO"<<endl
#define yes cout<<"yes"<<endl
#define no cout<<"no"<<endl
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl

#define SP cout << " ";
#define ENDL cout << "\n";
#define outp(i) cout << (i);
#define outps(i) cout << (i) << " ";
#define outpl(i) cout << (i) << "\n";
#define setfp() cout << fixed << setprecision(16)

template<typename C>
void outpv(C &v){for(auto &&e:v){cout << e;if(&e != &v.back()) cout << ' ';}cout << "\n";}

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

inline ll lg(ll __n) { return sizeof(ll) * __CHAR_BIT__ - 1 - __builtin_clzl(__n); }

int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

int main(){
    inp(N);
    long double F = 2.18169499062491237350;
    setfp();
    outpl(N*N*N*F);

    return 0;
}