# ifndef ONLINE_JUDGE
# define _GLIBCXX_DEBUG
# endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
# define rep(i, n) for(int i = 0; i < (int)(n); i++)
# define all(v) v.begin(), v.end()

vi eratosthenes(int N){
  vector<bool> flag(N+1, true);
  vi prime(0);
  flag[0] = false;  flag[1] = false;
  rep(p, N+1){
    if(flag[p]){
      prime.push_back(p);
      for(int i = p*p; i <=N; i += p){
        flag[i] = false;
      }
    }
  }
  return prime;
}
int main(){
  constexpr char endl = '\n';
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(10);
  //input();
  int N;cin >> N;
  //solve();
  vi p = eratosthenes(N);
  vvi dp(p.size()+1, vi(N+1, -1));
  //dp[i+1][j]:=i番目の素数まで使ったとき、和としてjを作るとき、足す回数の最大値
  dp[0][0] = 0;
  rep(i, p.size()){
    for(int j = 0; j <= N; ++j){
      if(0 <= j-p[i] && dp[i][j-p[i]] != -1)  dp[i+1][j] = max(dp[i+1][j], dp[i][j-p[i]]+1);
      if(dp[i][j] != -1)  dp[i+1][j] = max(dp[i+1][j], dp[i][j]);
    }
  }
  //output();
  cout << dp[p.size()][N] << endl;
}