#include <bits/stdc++.h>

#include <atcoder/all>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
using namespace atcoder;
using namespace std;

typedef long long ll;

double eps = 1e-12;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(5);
    ll c;
    cin >> c;
    auto check = [&](double x) {
        double y = x * x * x * x * x + x - c;
        if (y <= 0) return 1;
        return 0;
    };
    auto binary = [&]() {
        int trial_ct = 80;
        double L = 0.0, R = 2000000010.0;
        double mid = L + (R - L) / 2.0;
        while (trial_ct--) {
            if (check(mid))
                L = mid;
            else
                R = mid;
            mid = L + (R - L) / 2.0;
        }
        return mid;
    };
    double ans = binary();
    ans += eps;
    ans = floor(ans * 1000) / 1000;
    printf("%.3f\n", ans);
}