3968. Square root

#include <bits/stdc++.h>

using namespace std;

#define int long long
#define mp make_pair
#define pb push_back

const long double eps = 1e-7;

signed main() {
    ios::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr);
    //freopen("input.txt","r",stdin);
    //freopen("output.txt","w",stdout);

    long double C;
    cin >> C;

    long double L = 0,R = (int)1e9;
    long double mid;

    while(R-L>eps)
    {
        mid = (L+R)/2;
        if(mid*mid + sqrt(mid) > C)
            R = mid;
        else
            L = mid;
    }

    cout << fixed << setprecision(8) << (L+R)/2;

    return 0;
}