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

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    double N; cin >> N;
    N = N*N*N;

    double answer = 0,dx = 0.000001,back = sqrt(N);
    for(double x=0; x<1; x+=dx){
        double next = sqrt(x*x*x+N);
        answer += (back+next)/2*dx;
        back = next;
    }
    cout << fixed << setprecision(20) << answer << endl;
}