#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int (i)=(0);(i)<(int)(n);++(i))
using ll = long long;
using P = pair<int, int>;
using namespace std;

template<class T> void vin(vector<T>& v, int n) {
    v.resize(n);
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
    }
}

vector<int> prime;
bool not_prime[20001];
int N;

int dp[2500][20001];

int eratos(int n) {
    not_prime[0] = not_prime[1] = true;
    for (int i = 2; i <= n; ++i) {
        if (!not_prime[i]) {
            prime.push_back(i);
            for (int j = 2 * i; j <= n; j += i) not_prime[j] = true;
        }
    }
}

int rec(int i, int k) {
    int res;
    if (dp[i][k] != -1) return dp[i][k];
    if (k == N) res = 0;
    else if (i >= (int)prime.size() or k > N) res = -1e8;
    else if (k + prime[i] <= N) {
        res = max(rec(i+1, k), rec(i + 1, k + prime[i]) + 1);
    } else {
        res = -1e8;
    }
    return (dp[i][k] = res);
}

int main() {
    cin >> N;
    eratos(N);
    fill(dp[0], dp[prime.size() + 10], -1);
    int ans = rec(0, 0);
    cout << (ans > 0 ? ans : -1) << endl;
    return 0;
}