#include <iostream>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <string>
#include <map>
#include <queue>
#define ll long long

int main() {
  ll N;
  std::cin >> N;
  ll ss = sqrt(N)+1L;
  ll ans = -1L;
  for(ll i = 3L; i <= ss; i++) {
    if(N % i == 0L) {
      ans = i;
      break;
    }
  }
  if(ans == -1L) {
    ans = N;
  }
  if(N % 2 == 0 && N >= 6) {
    ans = std::min(ans,N/2);
  }
  std::cout << ans << std::endl;
}