#include <bits/stdc++.h>

using namespace std;

int dp[20001];
long long sumprime;

void hawawa()
{
	int n;
	cin >> n;
	memset(dp, -1, sizeof(dp));
	dp[2] = 1;
	vector<int> prime(2);
	vector<bool> is_prime(n + 1, true);
	is_prime[0] = is_prime[1] = false;
	for (int i = 3; i * i <= n; i += 2) {
		if (is_prime[i]) {
			for (int j = i * i; j <= n; j += i) {
				is_prime[j] = false;
			}
		}
	}
	for (int i = 3; i <= n; i += 2) {
		if (is_prime[i]) {
			prime.push_back(i);
			dp[i] = 1;
		}
	}
	for (int i = 0; i < prime.size(); i++) {
		sumprime += prime[i];
		for (int j = 2; j + prime[i] <= sumprime && j + prime[i] <= n; j++) {
			if (dp[j] == -1 || j == prime[i]) continue;
			dp[j + prime[i]] = max(dp[j + prime[i]], dp[j] + 1);
		}
	}
	cout << dp[n] << "\n";
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	hawawa();
	return 0;
}