#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef long int li;
typedef long double lb;
#define rep(i,j,n) for (ll i = j; i < (n); i++)
#define all(x) (x).begin(),(x).end()
#define CLR(mat,f) memset(mat, f, sizeof(mat))
#define IN(a, b, x) (a<=x&&x<b)
#define out(ans) cout << ans << endl
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; }
typedef pair<ll,ll>P;
const ll mod=1e9+7;
const int INF = 1000000;
const double PI=3.14159265359;

int main(){

  ll n;cin>>n;

  bool is_prime[n+1];CLR(is_prime,true);
  is_prime[0]=is_prime[1]=false;

  vector<ll>prime;
  for(ll i=2;i<=n;i++){
    if(is_prime[i]){
      prime.push_back(i);
      for(ll j=2;i*j<=n;j++){
        is_prime[i*j]=false;
      }
    }
  }

  ll dp[20002];
  CLR(dp,-1);
  dp[0]=0;
  rep(i,0,prime.size()){
    for(ll j=n;j>=prime[i];j--){
      if(dp[j-prime[i]]!=-1)chmax(dp[j],dp[j-prime[i]]+1);
    }
  }
  out(dp[n]);

  return 0;
}