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

int main()
{
	int N;
	cin >> N;
	vector<bool> Is(N + 1, true);
	Is[0] = Is[1] = false;
	for (int i = 2; i * i <= N; i++) {
		if (Is[i]) {
			for (int j = i * 2; j <= N; j += i) {
				Is[j] = false;
			}
		}
	}
	vector<int> dp(N + 1);
	dp[N] = 1;
	for (int i = 2; i <= N; i++) {
		if (Is[i]) {
			for (int j = i; j <= N; j++) {
				if (dp[j]) {
					dp[j - i] = max(dp[j - i], dp[j] + 1);
				}
			}
		}
	}
	cout << dp[0] - 1 << endl;
	return 0;
}