#ifndef LOCAL
#include <bits/stdc++.h>

using namespace std;

#define debug(...) (void(0))
#else
#include "algo/debug.h"
#endif

#include <atcoder/internal_math>
void solve() {
    int N;
    cin >> N;
    vector<int> P;
    P.reserve(3000);
    const int M = 20000;
    for (int i = 1; i <= min(M, N); i++)
        if (atcoder::internal::is_prime_constexpr(i)) P.push_back(i);
    vector<int> dp(N + 1, -1);
    dp[0] = 0;
    for (unsigned i{}; i < P.size(); i++) {
        for (int j = N + 1; j >= 0; j--)
            if (j - P[i] >= 0 && dp[j - P[i]] != -1) {
                dp[j] = max(dp[j], dp[j - P[i]] + 1);
            }
    }
    cout << dp[N] << endl;
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int tt = 1;
    // std::cin >> tt;
    while (tt--) {
        solve();
    }
}