#include <bits/stdc++.h>
#define REP(i, s, n) for (int i = s; i < n; i++)
#define ALL(a) a.begin(), a.end()
#define MOD 1000000007
using namespace std;
typedef long long ll;

vector<bool> Eratosthenes(int n) {
    vector<bool> prime(n, true);
    prime[0] = prime[1] = false;
    for (int i = 2; i * i <= n; i++) {
        if (!prime[i]) continue;
        for (int j = 2; i * j <= n; j++) {
            prime[i * j] = false;
        }
    }
    return prime;
}

int main() {
    int N; cin >> N;
    vector<bool> prime(N + 1, true);
    for (int i = 2; i * i <= N; i++) {
        if (!prime[i]) continue;
        for (int j = 2; i * j <= N; j++) prime[i * j] = false;
    }

    vector<int> primes;
    REP(i, 2, N + 1) if (prime[i]) primes.push_back(i);

    vector<vector<int>> dp(primes.size() + 1, vector<int>(N + 1, -1));
    dp[0][0] = 0;
    REP(i, 0, primes.size()) {
        REP(j, 0, N + 1) {
            if (dp[i][j] == -1) continue;
            dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
            if (j + primes[i] <= N) dp[i + 1][j + primes[i]] = max(dp[i + 1][j + primes[i]], dp[i][j] + 1);
        }
    }
    cout << dp[primes.size()][N] << endl;
    return 0;
}