#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

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

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

vector<bool> isprime;

void eratos(ll n) {
	isprime.resize(n + 1);
	for (ll i = 0; i <= n; i++) {
		isprime[i] = true;
	}
	isprime[0] = false;
	isprime[1] = false;
	for (ll i = 2; i * i <= n; i++) {
		if (isprime[i]) {
			ll j = i + i;
			while (j <= n) {
				isprime[j] = false;
				j = j + i;
			}
		}
	}
}

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	ll N; scanf("%lld", &N);
	eratos(N + 100);
	vector<ll> dp(N + 1, -1);
	vector<ll> pr;
	dp[0] = 0;
	for (ll i = 2; i <= N; i++) if (isprime[i]) pr.push_back(i);

	for (ll e : pr) {
		vector<ll> tmp(N + 1, -1);
		tmp[0] = 0;
		for (ll i = 0; i <= N; i++) {
			chmax(tmp[i], dp[i]);
			if (dp[i] == -1) continue;
			if (i + e > N) continue;
			chmax(tmp[i + e], dp[i] + 1);

			//cout << i << " " << tmp[i] << endl;
		}
		dp = tmp;
		
	}

	cout << dp[N] << endl;
	return 0;
}