#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;

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