#include #include using namespace std; // using mint = long double; // using mint = modint998244353; // using mint = modint1000000007; typedef long long ll; typedef pair P; typedef pair T; typedef pair> Pd; const ll INF = 4e18; const ll fact_table = 1200008; priority_queue pql; priority_queue

pqp; // big priority queue // priority_queue , greater > pqls; priority_queue, greater

> pqps; // small priority queue // top pop ll dx[8] = {1, 0, -1, 0, 1, 1, -1, -1}; ll dy[8] = {0, 1, 0, -1, -1, 1, 1, -1}; //↓,→,↑,← /* #define endl "\n" #ifdef ENJAPMA #undef endl #endif */ #define p(x) cout << x << endl; #define el cout << endl; #define pe(x) cout << x << " "; #define ps(x) cout << fixed << setprecision(25) << x << endl; #define pu(x) cout << (x); #define pb push_back #define lb lower_bound #define ub upper_bound #define pc(x) cout << x << ","; #define rep(i, n) for (ll i = 0; i < (n); i++) #define rep2(i, a, b) for (ll i = a; i <= (b); i++) #define rep3(i, a, b) for (ll i = a; i >= (b); i--) #define all(c) begin(c), end(c) typedef vector vec; typedef vector> mat; // vec v(n) -> 長さnのベクトルを宣言 // mat dp(h, vec(w)) -> h * w の行列を宣言 const ll mod = 998244353ll; // const ll mod = 1000000007ll; ll mypow(ll a, ll b, ll m = mod) { ll x = 1; while (b) { while (!(b & 1)) { (a *= a) %= m; b >>= 1; } (x *= a) %= m; b--; } return x; } vec rv(ll read) { vec res(read); for (int i = 0; i < read; i++) { cin >> res[i]; } return res; } /* ll fact[fact_table + 5], rfact[fact_table + 5]; void c3_init() { fact[0] = rfact[0] = 1; for (ll i = 1; i <= fact_table; i++) { fact[i] = (fact[i - 1] * i) % mod; } rfact[fact_table] = mypow(fact[fact_table], mod - 2, mod); for (ll i = fact_table; i >= 1; i--) { rfact[i - 1] = rfact[i] * i; rfact[i - 1] %= mod; } return; } ll c3(ll n, ll r) { return (((fact[n] * rfact[r]) % mod) * rfact[n - r]) % mod; } */ bool icpc = false; bool multicase = false; ll n, k; ll cost[200005]; bool solve() { long double x; cin >> x; x *= 4.0; ps(x / 3.14159265359); return true; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); if (icpc) { while (solve()) ; return 0; } ll q, testcase = 1; if (multicase) { cin >> q; } else { q = 1; } while (q--) { solve(); testcase++; } // solve(); return 0; }