#include <iostream>
#include <vector>
using namespace std;
using vi = vector<int>;

#define rep(i,n) for(int i=0,_i=(n);i<_i;++i)

template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
bool is_prime[20001];
int dp[3000][20001];
int main() {
  int N; cin >> N;

  rep(i, N+1) is_prime[i] = true;
  is_prime[0] = is_prime[1] = false;

  for (int i = 2; i * i <= N; ++i) {
    if (!is_prime[i])
      continue;
    for (int j = i*i; j <= N; j += i)
      is_prime[j] = false;
  }

  vi prime;
  rep(i, N+1)
    if (is_prime[i])
      prime.push_back(i);

  rep(i, 3000) rep(w, N+1)
    dp[i][w] = w == 0 ? 0 : -1;

  rep(i, prime.size()) rep(w, N+1) {
    dp[i+1][w] = dp[i][w];
    if (w-prime[i] >= 0 && dp[i][w-prime[i]] >= 0)
      dp[i+1][w] = max(dp[i+1][w], dp[i][w-prime[i]]+1);
  }
  cout << dp[prime.size()][N] << endl;
}