#include <bits/stdc++.h>
using namespace std;

// #define int long long
#define rep(i, n) for (long long i = (long long)(0); i < (long long)(n); ++i)
#define reps(i, n) for (long long i = (long long)(1); i <= (long long)(n); ++i)
#define rrep(i, n) for (long long i = ((long long)(n)-1); i >= 0; i--)
#define rreps(i, n) for (long long i = ((long long)(n)); i > 0; i--)
#define irep(i, m, n) for (long long i = (long long)(m); i < (long long)(n); ++i)
#define ireps(i, m, n) for (long long i = (long long)(m); i <= (long long)(n); ++i)
#define SORT(v, n) sort(v, v + n);
#define REVERSE(v, n) reverse(v, v+n);
#define vsort(v) sort(v.begin(), v.end());
#define all(v) v.begin(), v.end()
#define mp(n, m) make_pair(n, m);
#define cout(d) cout<<d<<endl;
#define coutd(d) cout<<std::setprecision(10)<<d<<endl;
#define cinline(n) getline(cin,n);
#define replace_all(s, b, a) replace(s.begin(),s.end(), b, a);
#define PI (acos(-1))
#define FILL(v, n, x) fill(v, v + n, x);
#define sz(x) long long(x.size())

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vs = vector<string>;
using vpll = vector<pair<ll, ll>>;
using vtp = vector<tuple<ll,ll,ll>>;
using vb = vector<bool>;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const ll INF = 1e9+10;
const ll MOD = 1e9+7;
const ll LINF = 1e18;

const ll maxn_eratosthenes = 100005;
bool _is_prime[maxn_eratosthenes];
vector<ll> P;

void eratosthenes(const ll N)
{
  P.clear();
  for (ll i = 0; i <= N; i++) {
    _is_prime[i] = true;
  }
  _is_prime[0]=_is_prime[1]=false;
  for (ll i = 2; i <= N; i++) {
    if (_is_prime[i]) {
      for (ll j = 2 * i; j <= N; j += i) {
        _is_prime[j] = false;
      }
      P.emplace_back(i);
    }
  }
}

ll dp[3000][20005];

signed main()
{
  cin.tie( 0 ); ios::sync_with_stdio( false );
  ll n; cin>>n;
  eratosthenes(n);
  // cout<<P.size()<<endl;
  // rep(i,P.size()) cout<<P[i]<<endl;
  
  ll m=P.size();
  
  vll dp(n+1,-INF);
  dp[0]=0;
  
  for(ll i=0; i<m; i++){
    vll ndp=dp;
    for(ll j=0; j<=n; j++){
      if(P[i]+j<=n) {
        chmax(ndp[P[i]+j],dp[j]+1);
      }
    }
    dp=move(ndp);
  }
  
  if(dp[n]>0) cout<<dp[n]<<endl;
  else cout<<-1<<endl;
  
}