#include<iostream>
using namespace std;

int main(){
        long long n;
        cin >> n;

        for(long long i = 3; i*i <= n; i++){
                if(n % i == 0){
                        cout << i << endl;
                        return 0;
                }
        }

        if( n % 2 == 0 && n != 4){
                cout << n / 2 << endl;
        }else{
                cout << n << endl;
        }
}