#include <algorithm>
#include <iomanip>
#include <iostream>
#include <vector>
using namespace std;
#define MAX_N 20001
int N;
// int dp[MAX_N + 10][MAX_N + 10];
vector<int> sieve(int n) {
    vector<int> prime;
    vector<bool> is_prime(n + 1, true);
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i <= n; ++i) {
        if (is_prime[i]) {
            prime.push_back(i);
            for (int j = 2 * i; j <= n; j += i) { is_prime[j] = false; }
        }
    }
    return prime;
}

int main() {
    cin >> N;
    // if (N == 1) {
    //     cout << -1 << endl;
    //     return 0;
    // }
    vector<int> prime   = sieve(N);
    int number_of_prime = prime.size();

    vector<vector<int>> dp(N + 1, vector<int>(number_of_prime + 1, -1));
    for (int i = 0; i <= 0; i++) {
        for (int j = 0; j <= number_of_prime; j++) { dp[i][j] = 0; }
    }

    for (int i = 0; i <= N; i++) {
        for (int j = 0; j < number_of_prime; j++) {
            dp[i][j + 1] = dp[i][j];
            if (i - prime[j] >= 0 && dp[i - prime[j]][j] != -1) {
                dp[i][j + 1] = max(dp[i][j + 1], dp[i - prime[j]][j] + 1);
            }
        }
    }
    // for (int i = 0; i <= N; i++) {
    //     for (int j = 0; j < number_of_prime; j++) {
    //         cout << setw(3) << dp[i][j];
    //     }
    //     cout << endl;
    // }

    cout << dp[N][number_of_prime] << endl;

    return 0;
}
// dp[i][j]は和がiになるもので、j番目の要素まで使った場合の最大の素数の数
// dp[i][j]=max(dp[i][j-1],dp[i-xj][j-1]+1);