#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>

using namespace std;

int N;
int isprime[20010];
int dp[20010];

void eratos(int m)
{

    for (int i = 0; i <= m; i++)
        isprime[i] = true;
    isprime[0] = isprime[1] = false;

    for (int i = 2; i <= m; ++i)
    {
        if (isprime[i])
        {
            for (int j = 2 * i; j <= m; j += i)
                isprime[j] = false;
        }
    }
}

int main()
{
    cin >> N;
    eratos(N);
    vector<int> primes;

    for (int i = 2; i < N + 1; i++)
    {
        if (isprime[i])
            primes.push_back(i);
    }

    memset(dp, -1, sizeof(dp));

    dp[0] = 0;

    for (auto p : primes)
    {
        for (int i = N; i >= 0; i++)
        {
            if (i - p < 0 || dp[i - p] < 0)
                continue;
            dp[i] = max(dp[i], dp[i - p] + 1);
        }
    }

    cout << dp[N] << endl;

    return 0;
}