#include <iostream>
#include <math.h>
using namespace std;
typedef long long LL;
using namespace std;
int main(int argc, char* argv[])
{
	LL N;
	cin>>N;
	if (N%3==0){
		cout<<3<<endl;
		return 0;
	}
	LL n=sqrt((double)N);
	LL i;
	for (i=3;i<=n;i++){
		if (N%i==0){
			cout<<i<<endl;
			return 0;
		}
	}
	cout<<N<<endl;
	return 0;
}