#include <bits/stdc++.h>
const double PI = 3.141592653589793238460;
using namespace std;
long long pows(long long a, long long n, long long m) {
  a = a % m;
  long long res = 1;
  while (n) {
    if (n % 2 != 0) {
      res = (res * a) % m;
      n--;
    } else {
      a = (a * a) % m;
      n = n / 2;
    }
  }
  return res % m;
}
long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
bool isprime(long long n) {
  if (n == 1 || n == 0) {
    return false;
  }
  for (long long i = 2; i * i <= n; i++) {
    if (n % i == 0) {
      return false;
    }
  }
  return true;
}
bool istrue(string s) {
  int i = 0;
  int j = s.size() - 1;
  while (i < j) {
    if (s[i] == s[j]) {
      i++;
      j--;
    } else {
      return false;
    }
  }
  return true;
}
const int N = 200005;
long long flag = 0;
long long m;
bool fun(long long val) {
  long long w = cbrt(val);
  long long ans = 0;
  for (long long i = 2; i <= w; i++) {
    long long v = pow(i, 3LL);
    ans += val / v;
  }
  if (ans == m) {
    flag = 1;
  }
  if (ans >= m) {
    return true;
  }
  return false;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long TT = clock();
  cin >> m;
  long long l = 1;
  long long r = 1e16;
  while (l + 1 < r) {
    long long mid = (l + r) / 2;
    if (fun(mid) == true) {
      r = mid;
    } else {
      l = mid;
    }
  }
  if (flag == 0) {
    cout << -1 << "\n";
    return 0;
  }
  cout << r << "\n";
  cerr << "\n\nTIME: " << (long double)(clock() - TT) / CLOCKS_PER_SEC
       << " sec\n";
  TT = clock();
  return 0;
}
