#include <iostream>
#include <iomanip>
#include <cmath>

int main()
{
    auto x{ 0.0 },
        e{ 0.0 };
    auto n{ 3 };

    std::cin >> x >> e;

    auto yr{ x }, yr2{ std::pow(x, n) / n };
    auto sum{ 0.0 };

    while (std::abs(yr2 - yr) >= e)
    {
        sum += yr;

        yr = yr2;

        n += 2;

        yr2 = std::pow(x, n) / n;
    }

    std::cout << std::fixed << std::setprecision(6) << sum;
}