#include <iostream>
#include <vector>
#include <cstring>
using namespace std;

bool is_prime(int n) {
    if (n <= 1) return false;
    for (int m = 2; m * m <= n; m++) {
        if (n % m == 0) return false;
    }
    return true;
}

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

    vector<int> primes;
    for (int n = 2; n <= 20000; n++) {
        if (is_prime(n)) primes.emplace_back(n);
    }

    static int dp[30000];
    memset(dp, -1, sizeof(dp));
    dp[0] = 0;

    for (int p : primes) {
        for (int i = N; i >= 0; i--) {
            if (i - p < 0 or dp[i - p] < 0) continue;
            dp[i] = max(dp[i], dp[i - p] + 1);
        }
    }
    cout << dp[N] << endl;

    return 0;
}