#include<limits>
using ll=long long;constexpr int INF=std::numeric_limits<int>::max()/2;constexpr ll LNF=std::numeric_limits<ll>::max()/2;constexpr double EPS=1e-8;constexpr int DX[]={1,0,-1,0,1,1,-1,-1};constexpr int DY[]={0,1,0,-1,-1,1,1,-1};
#ifdef PA_DEBUG
#define PD(stmt)stmt
#else
#define PD(stmt)
#endif
#include<iostream>
#include<vector>
namespace pcl{namespace utility{template<typename T>std::ostream&operator<<(std::ostream&os,std::vector<T>const&v){os<<'[';for(size_t i=0;i<v.size();i++){if(i!=0)os<<",";os<<v[i];}os<<']';return os;}template<typename T>std::istream&operator>>(std::istream&is,std::vector<T>&v){for(size_t i=0;i<v.size();i++)is>>v[i];return is;}}}using namespace pcl::utility;
#include<algorithm>
#include<iomanip>
#include<iostream>
#include<vector>
using namespace std;
#define MAX_N 20001
int N;vector<int>sieve(int n){vector<int>prime;vector<bool>is_prime(n+1,true);is_prime[0]=is_prime[1]=false;for(int i=2;i<=n;++i){if(is_prime[i]){prime.push_back(i);for(int j=2*i;j<=n;j+=i){is_prime[j]=false;}}}return prime;}int main(){cin>>N;vector<int>prime=sieve(N);int number_of_prime=prime.size();vector<vector<int>>dp(N+1,vector<int>(number_of_prime+1,-1));for(int i=0;i<=0;i++){for(int j=0;j<=number_of_prime;j++){dp[i][j]=0;}}for(int i=0;i<=N;i++){for(int j=0;j<number_of_prime;j++){dp[i][j+1]=dp[i][j];if(i-prime[j]>=0&&dp[i-prime[j]][j]!=-1){dp[i][j+1]=max(dp[i][j],dp[i-prime[j]][j]+1);}}}cout<<dp[N][number_of_prime]<<endl;return 0;}