#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)
#define all(x) begin(x), end(x)

template <class T> bool chmin(T& x, T y) {
	return x > y ? (x = y, true) : false;
}
template <class T> bool chmax(T& x, T y) {
	return x < y ? (x = y, true) : false;
}

struct io_setup {
	io_setup() {
		ios::sync_with_stdio(false);
		cin.tie(nullptr);
		cout << fixed << setprecision(15);
	}
} io_setup;

using mint = atcoder::modint998244353;
using i128 = __int128_t;

void solve() {
	ll c;
	cin >> c;
	c *= (ll)1e15;
	auto check = [&](ll x) {
		ll p5 = x * x * x * x * x;
		x *= (ll)1e12;
		return (p5 + x - c > 0);
	};
	auto print_ans = [&](ll x) {
		string s = to_string(x);
		while (s.size() < 4) s.insert(s.begin(), '0');
		s.insert(s.end() - 3, '.');
		cout << s << '\n';
	};
	rep(i, 0, 10000) {
		if (check(i + 1)) {
			print_ans(i);
			break;
		}
	}
}

int main() {
	int t = 1;
	// cin >> t;
	while (t--) solve();
}