#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <utility>
#include <stack>
#include <functional>
#include <queue>
#include <cmath>
#include <set>
#include <map>

#define rep(i,j,k) for(int i=(int)j;i<(int)k;i++)
#define Sort(x) sort((x).begin(),(x).end())
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define vi vector<int>
#define INF (int)1e933
#define INFL 1e18
#define MOD 1e9+7
#define pb push_back
#define MP make_pair
typedef long long ll;
typedef std::pair<int,int> pii;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};

using namespace std;

bool isPrime(int x){
    if(x==1)return false;
    if(x==2)return true;
    if(x%2==0)return false;
    for(int i=3;i*i<=x;i+=2){
        if(x%i==0)return false;
    }
    return true;
}

int main() {
    int n;cin>>n;
    vector<int> v;
    rep(i,1,20001){
        if(i%2==0)continue;
        if(isPrime(i))v.pb(i);
    }
    vector<vector<int>> dp((int)v.size()+1,vector<int>(20001,-1));
    dp[0][0]=0;
    rep(i,0,v.size()){
        rep(j,0,n+1){
            dp[i+1][j]=dp[i][j];
            
            if(j>=v[i]&&dp[i][j-v[i]]!=-1) dp[i+1][j]=max(dp[i][j-v[i]]+1,dp[i+1][j]);
        }
    }
    cout<<dp[(int)v.size()][n]<<endl;
    
    return 0;
}