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

void sieve(ll n, vector<ll>& ps, vector<bool>& is_prime) {
	ps = vector<ll>();
	is_prime = vector<bool>(n + 1, true);

	is_prime[0] = is_prime[1] = false;
	for(ll i = 2; i <= n; i++) {
		if(is_prime[i]) {
			ps.push_back(i);
			for(ll j = 2 * i; j <= n; j += i) {
				is_prime[j] = false;
			}
		}
	}
}

int dp[20010];

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

	int n;
	cin >> n;

	vector<bool> is_prime;
	vector<ll> ps;
	sieve(n, ps, is_prime);

	memset(dp, -1, sizeof dp);
	dp[0] = 0;
	for(int j = 0; j < ps.size(); j++) {
		for(int i = n - 1; i >= 0; i--) {
			if(dp[i] == -1) continue;
			if(i + ps[j] <= n) {
				dp[i + ps[j]] = max(dp[i + ps[j]], dp[i] + 1);
			}
		}
	}

	cout << dp[n] << endl;
}