#include <bits/stdc++.h>

using namespace std;

int count(int n) {
  int v = sqrt(n);
  vector<int> smalls(v + 1);
  vector<int> larges(v + 1);
  for (int i = 1; i <= v; ++i) {
    smalls[i] = i - 1;
  }
  for (int i = 1; i <= v; ++i) {
    larges[i] = n / i - 1;
  }
  for (int p = 2; p <= v; ++p) {
    if (smalls[p] == smalls[p - 1]) {
      continue;
    }
    int q = p * p, c = smalls[p - 1];
    int w = v / p, e = min(v, n / q);
    for (int i = 1; i <= w; ++i) {
      larges[i] -= larges[i * p] - c;
    }
    for (int m = n / p, i = w + 1; i <= e; ++i) {
      larges[i] -= smalls[m / i] - c;
    }
    for (int i = v; i >= q; --i) {
      smalls[i] -= smalls[i / p] - c;
    }
  }

  int ret = smalls[(int)cbrt(n)];
  for (int p = 2; p <= v; ++p) {
    if (smalls[p] != smalls[p - 1]) {
      ret += larges[p] - smalls[p];
    }
  }
  return ret;
}

int main() {
  int n, lo = 0, hi = 1e9;

  scanf("%d", &n);
  while (hi - lo > 1) {
    int mi = (lo + hi - 1) >> 1;
    if (count(mi) >= n) {
      hi = mi + 1;
    } else {
      lo = mi + 1;
    }
  }
  printf("%d\n", lo);

  return 0;
}