#include <iostream>
#include <iomanip>
#include <cassert>
#include <cmath>
const long double STEP{0.0000001};
int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);
    long double N;
    std::cin >> N;
    long double ans{};
    for (long double x{} ; x <= 1.0 ; x += STEP) {
        ans += STEP * sqrtl(x*x*x+N*N*N);
    }
    std::cout << std::fixed << std::setprecision(7) << ans << '\n';
}