#include<iostream>
#include<algorithm>
using namespace std;
using lint=int64_t;

int main()
{
	lint N;

	cin >> N;

	for(lint i=3;i*i<=N;i++)
	{
		if(N%i==0)
		{
			cout << i << endl;
			break;
		}
	}
	return 0;
}