#include<bits/stdc++.h>
using namespace std;
#ifdef LOCAL_DEBUG
  #include "LOCAL_DEBUG.hpp"
#endif
#define int long long

signed main(){

  int n; cin >> n;
  map<int ,int> mp;
  for(int i = 2; i*i <= n; i++){
    if(n % i == 0){
      mp[i]++;
    }
  }
  for(auto p : mp){
    if(p.first <= 2) continue;
    cout << p.first;
    return 0;
  }

  return 0;
}