#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <cmath>   
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
#define all(x) (x).begin(),(x).end()
#define rep(i,m,n) for(int i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(int i = m;i >= n;--i)
#define INF INT_MAX/2
using namespace std;
using ll = long long;
using R = double;
using Data = pair<ll, vector<int>>;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 50;
struct edge { ll from; ll to; ll cost; };

vector<int>pr;
int memo[20202];
int used[20202];

bool prime(ll n) {
	if (n == 1) {
		return false;
	}
	for (ll i = 2; i*i <= n; i++) {
		if (n%i == 0) {
			return false;
		}
	}
	return true;
}

void pri(int *x) {
	rep(i,0,11) {
		cout << " " << x[i];
	}
	cout << endl;
}


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

	rep(i, 0, n + 1)memo[i] = -1;
	for (int i = 2; i <= n; i++)if (prime(i))pr.pb(i);

	memo[0] = 0;
	fore(x, pr) {
		for (int i = n; i >= 0; i--) {
			if (memo[i] == -1)continue;
			if (i+x <= n) {
				memo[i + x] = max(memo[i + x], memo[i] + 1);
			}
		}
	}
	cout << memo[n] << endl;


	return 0;
}