#include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr ll inf = (1LL << 62);
template <typename T>
bool chmax(T& a, const T& b)
{
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T>
bool chmin(T& a, const T& b)
{
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
long is_prime[20010];
vector<ll> primes;
void euclid()
{
    is_prime[0] = 2;
    is_prime[1] = 2;
    for (ll i = 2; i < 20010; ++i) {
        if (is_prime[i] == 0) {
            is_prime[i] = 1;
            primes.push_back(i);
            for (ll j = 2 * i; j < 20010; j += i) {
                is_prime[j] = 2;
            }
        }
    }
}

ll dp[20010];
int main()
{
    ll n;
    cin >> n;
    euclid();
    memset(dp, -1, 20010 * sizeof(long));
    dp[0] = 0;
    for (auto& p : primes) {
        for (ll i = n; i >= 0; --i) {
            if (p > i)
                break;
            if (dp[i - p] == -1)
                continue;
            chmax(dp[i], 1 + dp[i - p]);
        }
    }
    cout << dp[n] << endl;
}