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

using isize = size_t;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;
using f64 = long double;
using p2 = pair<i64, i64>;
using el = tuple<i64, i64, i64>;
using mint = atcoder::modint998244353;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(18);
  _main();
}

i64 pow(i64 x, i64 n) {
  i64 res = 1;
  i64 t = x;
  while (n > 0) {
    if (n & 1) {
      res = res * t;
    }
    t = t * t;
    n >>= 1;
  }
  return res;
}
i64 pow(i64 x, i64 n, i64 m) {
  i64 res = 1;
  i64 t = x % m;
  while (n > 0) {
    if (n & 1) {
      res = res * t % m;
    }
    t = t * t % m;
    n >>= 1;
  }
  return res;
}

void _main() {
  i64 c;
  cin >> c;
  i64 d = 1000;
  i64 l = 0, r = 4000;
  while (r - l > 1) {
    i64 mid = (l + r) / 2;
    i64 D = 1; 
    for (i64 i = 0; i < 5; i++) D *= d;
    i64 a = 1;
    for (i64 i = 0; i < 5; i++) a *= mid;
    i64 b = mid;
    for (i64 i = 0; i < 4; i++) b *= d;
    i64 cc = c;
    for (i64 i = 0; i < 5; i++) cc *= d;
    i64 s = a + b - cc;
    if (s <= 0) l = mid;
    else r = mid;
  }
  cout << l / d;
  cout << ".";
  string s = to_string(l % d);
  while (s.size() < 3) s = '0' + s;
  cout << s << "\n";
}