#include <bits/stdc++.h>
using namespace std;
int main() {
  long long m, s = -1, l = 1, r = 1e18;
  cin >> m;
  while (l <= r) {
    long long as = 0, i;
    long long mid = (l + r) / 2;
    for (i = 2; i * i * i <= mid; i++) as += mid / (i * i * i);
    if (as == m) s = mid;
    if (as >= m)
      r = mid - 1;
    else
      l = mid + 1;
  }
  cout << s;
}
