#include <iostream>
#include <cmath>
using namespace std;
typedef long long ll;

int main(){
  ll N;
  cin >> N;
  for(size_t i=3; i<=sqrt(N); i++){
    if(N % i == 0){
      cout << i << endl;
      return 0;
    }
  }
  if(N % 2 == 0){
    if(N == 4){
      cout << N << endl;
    }else{
      cout << N/2 << endl;
    }
  }else{
    cout << N << endl;
  }
  return 0;
}