#include <iostream>
#include <vector>
using namespace std;

int MakePrime(vector<int>& v, int n) {
    bool p[100001] = {1, 1};
    for(int i = 2; i <= n; i++) {
        if(p[i]) continue;
        v.push_back(i);
        for(int j = i * 2; j <= n; j += i)
            p[j] = true;
    }
    return v.size();
}

int main(void)
{
    const int maxdp = 20001;
    int n;
    vector<int> v;
    int dp[maxdp] = {1};
    int pn = MakePrime(v, 1000);
    cin >> n;
    for(int i = 0; i < pn; i++) {
        for(int j = maxdp - 1; j >= 0; j--) {
            if(dp[j] >= 1) {
                if(v[i] + j >= maxdp)
                    continue;
                dp[v[i] + j] = max(dp[v[i] + j], dp[j] + 1);
            }
        }
    }
    cout << dp[n] - 1 << endl;
    return 0;
}