#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];
    }
}

int N;
int p;

int prime[20101];
int not_prime[20101];

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

int dp[20000][20000];

int solve(int i, int sum) {
    int& res = dp[i][sum];
    if (~res) return res;
    if (sum == N) {
        res = 0;
    }
    else if (i >= p or sum + prime[i] > N) {
        res = -1e8;
    }
    else {
        res = max(solve(i+1, sum), solve(i+1, sum+prime[i]) + 1);
    }
    return res;
}

int main() {
    cin >> N;
    p = eratos(20000);
    sort(prime, prime+p);
    fill(dp[0], dp[p+10], -1);
    int tmp = solve(0, 0);
    cout << (tmp <= 0 ? -1 : tmp) << endl;
    return 0;
}