#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
using ll = long long;

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