#include <bits/stdc++.h>
using namespace std;
double f(double x)
{
    return 114 * x * x - 514 * x;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    const double eps = 1e-12;
    double l = 0;
    double r = 20;
    while (r - l > eps)
    {
        double L = (l + r) / 2;
        double R = (L + r) / 2;
        if (f(L) < f(R))
            r = R;
        else
            l = L;
    }
    cout << fixed << setprecision(10) << f(l);
    return 0;
}