/*
* @Author: kabbo
* @Date:   2020-06-24 08:40:07
* @Last Modified by:   kabbo
* @Last Modified time: 2020-06-24 08:49:58
*/
#include <bits/stdc++.h>
using namespace std;
#define pii pair<long long, long long>
#define endl '\n'
#define ull unsigned long long
#define ll int64_t
#define ar array
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0200r0.html
template <class Fun>
class y_combinator_result
{
    Fun fun_;

public:
    template <class T>
    explicit y_combinator_result(T &&fun) : fun_(std::forward<T>(fun)) {}

    template <class... Args>
    decltype(auto) operator()(Args &&...args)
    {
        return fun_(std::ref(*this), std::forward<Args>(args)...);
    }
};

template <class Fun>
decltype(auto) y_combinator(Fun &&fun)
{
    return y_combinator_result<std::decay_t<Fun>>(std::forward<Fun>(fun));
}
//const int mod = 1e9 + 7;
using u64 = uint64_t;
using u128 = __uint128_t;
#define sc1(x) scanf("%lld", &(x));
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
void dbg_out() { cerr << endl; }
template <typename Head, typename... Tail>
void dbg_out(Head H, Tail... T)
{
    cerr << ' ' << H;
    dbg_out(T...);
}
#ifndef NEAL_DEBUG
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif
/*Well, probably you won't understand anything,
because you didn't try to understand anything in your life,
you expect all hard work to be done for you by someone else. 
Let's start*/
const int X = 20000;

bitset<X> is_prime;
vector<int> pf;
vector<int> pr;

void init()
{
    pf.resize(X, 0);
    is_prime.flip();
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i < X; i++)
    {
        if (is_prime[i])
        {
            pr.push_back(i);
            pf[i] = i;
        }
        for (int p : pr)
        {
            if (ll(i) * p >= X)
                break;
            pf[i * p] = p;
            is_prime[i * p] = false;
            if (i % p == 0)
                break;
        }
    }
}

void solve()
{
    int n;
    cin >> n;
    int sz = pr.size();
    // dbg(sz);
    vector memo(sz + 5, vector(X + 1, (int)-1));
    auto dp = y_combinator(
        [&](auto self, int st, int n) -> int
        {
            if (n < 0)
                return -(int)1e5;
            if (st == sz)
            {
                if (n == 0)
                    return 0;
                else
                    return -(int)1e5;
            }
            int &res = memo[st][n];
            if (res != -1)
                return res;
            int a1 = 1 + self(st + 1, n - pr[st]);
            int a2 = self(st + 1, n);
            return res = max(a1, a2);
        }

    );
    int ans = dp(0, n);
    cout << (ans < 1 ? -1 : ans) << endl;
}
int main()
{

    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    init();
    solve();
    return 0;
}