#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

vector<int> sieve(int n) {
	vector<int> res;
	vector<bool> is_prime(n + 1, true);
	
	is_prime[0] = is_prime[1] = false;
	
	for (int i = 2; i * i <= n; i++) if (is_prime[i]) {
		res.push_back(i);
		is_prime[i] = false;
		for (int j = 2; i * j <= n; j++) if (is_prime[i * j]) {
			is_prime[i * j] = false;
		}
	}
	
	REP(i, n + 1) if (is_prime[i]) res.push_back(i);
	sort(res.begin(), res.end());
	return res;
}

int dp[20001];

int main() {
	int n;
	cin >> n;
	
	vector<int> prime = sieve(n);
	
	memset(dp, -1, sizeof(dp));
	dp[0] = 0;
	
	REP(i, prime.size()) for (int j = 20000; j >= prime[i]; j--)
		if (dp[j - prime[i]] != -1) chmax(dp[j], dp[j - prime[i]] + 1);
	
	cout << dp[n] << endl;
	return 0;
}