#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A& a, const B& b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A& a, const B& b) { if (a > b) { a = b; return true; } return false; }
template <class T, class F>
T binarySearchDouble(T ok, T ng, const F& f, int counter = 100) {
	while (counter--) {
		T mid = (ok + ng) / 2;
		(f(mid) ? ok : ng) = mid;
	}
	return ok;
}
int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	long long c; cin >> c;
	rep(i, 15)c *= 10;
	auto f = [&](const long long x)->bool {
		long long val = x * x * x * x * x + x * 1000000000000;
		return val <= c;
	};
	auto ans = binarySearchDouble<long long>(0, 10 * 1000, f);
	auto s = to_string(ans);
	while (s.size() < 4)s = '0' + s;
	cout << s[0] << "." << s[1] << s[2] << s[3] << endl;
	return 0;
}