#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;

int n, dp[20005];

bool isPrime(int x) {
	if (x < 2) return false;
	for (int i = 2; i * i <= x; i++) {
		if (x % i == 0) return false;
	}
	return true;
}

vector<int> getPrimes(int n) {
	vector<int> ret;
	for (int i = 2; i <= n; i++) {
		if (isPrime(i)) ret.push_back(i);
	}
	return ret;
}

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n;
	vector<int> p = getPrimes(n);
	fill(dp, dp+n+1, -1);
	dp[0] = 0;
	for (int i = 0; i < p.size(); i++) {
		for (int j = n; j >= 0; j--) {
			if (dp[j] != -1 && j+p[i] <= n) dp[j+p[i]] = max(dp[j+p[i]], dp[j]+1);
		}
	}
	cout << dp[n] << endl;
	return 0;
}