#include <bits/stdc++.h>
using namespace std;
typedef long long LL;

LL Cxiv_Dxiv(LL n){
    for(LL i = 3; i*i < n; i++)if(n%i==0)return i;
    return n;
}
int main() {
    LL N;
    cin>>N;
    cout<<Cxiv_Dxiv(N)<<endl;
    return 0;
}