#include <iostream>
#include <algorithm>
using namespace std;
int64_t N,ans;
int main(){
  cin >> N;
  ans=N;
  if(N%2==0&&2<N/2)ans=N/2;
  for(int64_t i=3;i*i<=N;i++){
    if(N%i==0)ans=min(ans,i);
  }
  cout<<ans<<endl;
}