#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //#include //#include //#include //#include //#include //#include //#include //#include //#include //#if __cplusplus >= 201103L //#include //#include //#include //#include // //#define cauto const auto& //#else //#endif using namespace std; typedef long long ll; typedef pair pii; typedef pair pll; typedef vector vint; typedef vector > vvint; typedef vector vll, vLL; typedef vector > vvll, vvLL; #define VV(T) vector > template void initvv(vector > &v, int a, int b, const T &t = T()){ v.assign(a, vector(b, t)); } template void convert(const F &f, T &t){ stringstream ss; ss << f; ss >> t; } #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define reep(i,a,b) for(int i=(a);i<(b);++i) #define rep(i,n) reep((i),0,(n)) #define ALL(v) (v).begin(),(v).end() #define PB push_back #define F first #define S second #define mkp make_pair #define RALL(v) (v).rbegin(),(v).rend() #define DEBUG #ifdef DEBUG #define dump(x) cout << #x << " = " << (x) << endl; #define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl; #else #define dump(x) #define debug(x) #endif #define MOD 1000000007LL #define EPS 1e-8 #define INF 0x3f3f3f3f #define INFL 0x3f3f3f3f3f3f3f3fLL #define maxs(x,y) x=max(x,y) #define mins(x,y) x=min(x,y) void mainmain() { double x; cin >> x; int a = x; double b = x - a; double sum1 = 0; double sum2 = 0; int N = 1e5; reep(i, 1 + a, N) { sum1 += pow(1. / i, 2) * pow(1. / (1. + b / i), 2); } reep(i, 1, N) { sum2 += pow(1. / i, 2); } double ans = sum1 + pow(acos(-1), 2) / 6 - sum2; cout << ans << endl; } signed main() { ios_base::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20); mainmain(); }