#include<iostream>
#include<string>
using namespace std;
int main(){
    long long N;
    long long i;
    cin >> N;
    for(i=3;i*i<=N;i++){
        if(N%i == 0){
            cout << i << endl;
            return 0;
        }
    }
    if(N%2 == 0 && N/2 > 2) cout << N/2 << endl;
    else cout << N << endl;;
    return 0;
}