#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

constexpr int MAX = 20000;
int seive[MAX + 1];
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;

    vector<int> primes;
    for(int i = 2; i <= MAX; ++i){
        if(seive[i])    continue;
        seive[i] = i;
        primes.emplace_back(i);
        for(int j = i + i; j <= MAX; j += i){
            if(seive[j] == 0)   seive[j] = i;
        }
    }
    
    vector<int> dp(MAX + 1, -1);
    dp[0] = 0;
    for(auto p : primes){
        for(int i = MAX - p; i >= 0; --i){
            if(dp[i] == -1) continue;
            chmax(dp[i + p], dp[i] + 1);
        }
    }

    cout << dp[N] << endl;

    return 0;
}