//C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif
#if __cplusplus >= 201402L
#include <shared_mutex>
#endif
#if __cplusplus >= 201703L
#include <any>
#include <charconv>
// #include <execution>
#include <filesystem>
#include <optional>
#include <memory_resource>
#include <string_view>
#include <variant>
#endif
#if __cplusplus > 201703L
#include <barrier>
#include <bit>
#include <compare>
#include <concepts>
#if __cpp_impl_coroutine
#include <coroutine>
#endif
#include <latch>
#include <numbers>
#include <ranges>
#include <span>
#include <stop_token>
#include <semaphore>
#include <source_location>
#include <syncstream>
#include <version>
#endif
//C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

#include<atcoder/convolution>
using namespace atcoder;

//#define int ll

using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using uint = unsigned int;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;
using Graph = vector<vector<ll>>;

#define rep1(i, n) for(ll i = 0; i < (int)(n); i++)
#define rep2(i, a, b) for(ll i = (int)(a); i < (int)(b); i++)
#define rep3(i, a, b, c) for(ll i = (int)(a); i < (int)(b); i+=(int)(c))
#define rrep1(i, n) for(ll i = (int)(n); i >= 0; i--)
#define rrep2(i, a, b) for(ll i = (int)(b); i >= (int)(a); i--)
#define REP(i) for(ll i = 0; ; i++)
#define all(v) (v).begin(), (v).end()

template<class T> using pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> bool chmin(T &a, const T &b){ if(a > b){ a = b; return 1; } else return 0; }
template<class T> bool chmax(T &a, const T &b){ if(a < b){ a = b; return 1; } else return 0; }
template<class T> auto min(const T& a){ return *min_element(all(a)); }
template<class T> auto max(const T& a){ return *max_element(all(a)); }
template<class T> ll sum(const T& a){ return accumulate(all(a), 0LL); }
template<class T> ld dsum(const T& a){ return accumulate(all(a), 0.0L); }

const int MOD = 1000000007;
const int MMOD = 998244353;
const int MAX = 510000;
const ll INF = 1LL<<60;

ll gcd(ll a, ll b){ while(b){ ll c = b; b = a % b; a = c; } return a; }
ll lcm(ll a, ll b){ if(!a || !b) return 0; return a * b / gcd(a, b); }
ll POW(ll a, ll b){ ll ans = 1; while(b){ if(b & 1) ans *= a; a *= a; b /= 2; } return ans; }
ll MODPOW(ll a, ll b){ ll ret = 1; while(b){ if(b & 1) ret = ret*a%MOD; a = a*a%MOD; b /= 2;} return ret;}

long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

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

signed main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  COMinit();
  
  ll N; cin >> N;
  vector<ll> P;
  rep1(i, 20000){
    if(is_prime(i+1)==true) P.push_back(i+1);
  }
  ll dp[22000] = {};
  rep1(i, 22000) dp[i] = -1;
  dp[0] = 0;
  for(auto p : P)rrep1(i, N){
    if(i-p>=0 && dp[i-p] != -1) chmax(dp[i], dp[i-p]+1);
  }
  cout << dp[N] << endl;
}