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

//因数分解
map<int,int> prime_factor(int n){
  map<int,int> mp; //{約数,個数}
  for(int i = 2; i*i <= n; i++){
    while(n%i == 0){
      mp[i]++;
      n /= i;
    }
  }
  if(n != 1) mp[n] = 1; //n=素数
  return mp;
}

signed main(){

  int n; cin >> n;
  auto mp = prime_factor(n);
  for(auto p : mp){
    if(p.first <= 2) continue;
    cout << p.first;
    return 0;
  }

  return 0;
}