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

const int N = 20009;
vector<bool> isp(N,true);
void sieve(){
  isp[0] = false; isp[1] = false;
  for(int i=2; N>=i*i; ++i){
    if(isp[i]) for(int j=2; N>=i*j; ++j) isp[i*j] = false;
  }
}

int main(){
  int n; cin >> n;
  sieve();
  vector<int> pri;
  for(int i=0; N>=i; ++i) if(isp[i]) pri.push_back(i);
  int siz = pri.size();
  //i番目までの素数を使って作れるjの最大値
  int dp[siz+1][n+1];
  for(int i=0; siz>=i; ++i){
    for(int j=0; n>=j; ++j){
      dp[i][j] = -1;
    }
  }
  dp[0][0] = 0;
  for(int i=0; siz>i; ++i){
    for(int j=0; n>=j; ++j){
      if(dp[i][j] != -1){
        dp[i+1][j] = max(dp[i+1][j],dp[i][j]);
        if(j+pri[i]<=n) dp[i+1][j+pri[i]] = max(dp[i+1][j+pri[i]],dp[i][j]+1);
      }
    }
  }
  int ans=-1;
  for(int i=0; siz>=i; ++i) ans = max(ans,dp[i][n]);
  cout << ans << endl;
}