#include <bits/stdc++.h>
typedef  long long ll;
#define INF 1000000000
using namespace std;
#define N 1000000
#define MOD 1000000007
int main(void){
    ll n;
    cin>>n;
    	for(ll i=3;i*i<=n;++i){
        if(n%i==0){
            cout<<i<<endl;
            return 0;
        }
    }
    cout<<n<<endl;
    
}