#include<iostream>
using namespace std;
int main(void)
{
	long long int i, n, ans;

	cin >> n;

	if (n % 3 == 0) {
		cout << 3 << endl;
		return 0;
	}
	if (n % 4 == 0) {
		cout << 4 << endl;
		return 0;
	}
	for (i = 5; i <= n; i+=2) {
		if (n%i == 0) {
			ans = i;
			break;
		}
	}
	cout << ans << endl;


	return 0;
}