#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;


class Primes {
public:
	int n;
	vector<int> primes;
	vector<bool> isPrime;

	Primes(int num) {
		n = num;
		calc();
	}

private:
	void calc() {
		isPrime.assign(n + 1, true);
		isPrime[0] = isPrime[1] = false;

		for (int i = 2; i * i <= n; i++) {
			if (isPrime[i]) {
				for (int j = i + i; j <= n; j += i) {
					isPrime[j] = false;
				}
			}
		}

		for (int i = 0; i <= n; i++) {
			if (isPrime[i]) {
				primes.emplace_back(i);
			}
		}
	}
};

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

	auto primes = Primes(n).primes;

	vector<int> dp(2*n + 1, -1);
	dp[0] = 0;
	for (auto pr : primes) {
		auto work = dp;
		for (int i = 0; i < n; i++) {
			if (dp[i] >= 0) {
				work[i + pr] = max(work[i + pr],  work[i] + 1);
			}
		}
		dp = work;
	}

	cout << dp[n] << endl;

	return 0;
}