#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
  ll n; cin >> n;
  ll ans = 0;
  for(ll i = 3; i*i <= n; i++){
    if(n%i==0){
      ans = i;
      break;
    }
  }
  if(ans==0){
    if(n%2==0) ans = n/2;
    else ans = n;
  }
  cout << ans << endl;
  return 0;
}