#include <bits/stdc++.h>
using namespace std;

#define pb         push_back

typedef long long ll;
const ll INF = 1000000000000000000ll;
const ll MOD = 1000000007ll;
const double EPS = 1e-8;

int dp[20001];

const int N = 20000;
bool is_prime[N+1];
vector<long long> prime;
void Eratos(){
	for(int i=0; i<N; i++){
		is_prime[i] = true;
	}
	is_prime[0] = is_prime[1] = false;
	for(int i=2; i<=N; i++){
		if(is_prime[i]){
			for(int j=2; i*j<=N; j++){
				is_prime[i*j] = false;
			}
		}
	}

	for(int i=2; i<=N; i++){
		if(is_prime[i]){
			prime.push_back(i);
		}
	}
}

int main(void) {
	//ios_base::sync_with_stdio(false);
	//cin.tie(0);
	Eratos();

	int n;
	cin >> n;

	for(int i=0; i<=n; i++){
		dp[i] = -1;
	}

	dp[0] = 0;
	for(int i=0; i<prime.size(); i++){
		for(int j=n; j>=0; j--){
			if(j-prime[i] >=0 && dp[j-prime[i]] >= 0){
				dp[j] = max(dp[j], dp[j-prime[i]] + 1);
			}
		}
	}

	/*
	for(int i=0; i<=n; i++){
		printf("%d ", dp[i]);
	}
	puts("");
	*/

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