#include <iostream>
#include <vector>
using namespace std;

int n;
vector<int> primes;

void setPrime(int n) {
	bool is_prime[20001] = {false};
	for (int i = 2; i <= n; i++) is_prime[i] = true;
	for (int i = 2; i <= n; i++) {
		if (is_prime[i]) {
			for (int j = i * 2; j <= n; j += i) {
				is_prime[j] = false;
			}
		}
	}
	for (int i = 2; i <= n; i++) {
		if (is_prime[i]) {
			primes.push_back(i);
		}
	}
}

int dp[20001][3001];	//dp[i][j] = 今までの和がiでj番目の素数から使えるときの,  今までの項数の最大値

int main() {
	cin >> n;
	setPrime(n);

	for (int i = 0; i <= n; i++) {
		for (int j = 0; j <= primes.size(); j++) {
			dp[i][j] = -114514;
		}
	}
	
	dp[0][0] = 0;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < primes.size(); j++) {
			//使わない
			dp[i][j + 1] = max(dp[i][j + 1], dp[i][j]);
			//使う
			if (i + primes[j] <= n) {
				dp[i + primes[j]][j + 1] = max(dp[i + primes[j]][j + 1], dp[i][j] + 1);
			}
		}
	}
	
	int ans = -1;
	for (int i = 0; i <= primes.size(); i++) {
		if (dp[n][i] > 0) {
			ans = max(ans, dp[n][i]);
		}
	}
	
	cout << ans << endl;
	return 0;
}