E OLYMP

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

int main()
{
    long double c;
    cin >> c;
    long double low = 0;
    long double high = 1e5;
    for(int i = 0; i < 40; i ++)
    {
        long double middle = (low + high) / 2;
        if(middle * middle + sqrt(middle) < c)
        {
            low = middle;
        }
        else
        {
            high = middle;
        }
    }
    cout.precision(9);
    cout << fixed << high << endl;
    return 0;
}