#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;}