#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repd(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define reps(i, a, n) for (int i = (int)(a); i < (int)(n); i++)
#define sortu(a) sort(a.begin(), a.end())
#define sortd(a) sort(a.rbegin(), a.rend())
#define YES(n) cout << ((n) ? "YES" : "NO") << endl
#define Yes(n) cout << ((n) ? "Yes" : "No") << endl
#define spaced(a) do {cout << a[0]; for (int _ = 1; _ < a.size(); _++) cout << " " << a[_]; cout << endl;} while (0)
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define mp make_pair
using vi = vector<int>;
using ll = long long;
using vvi = vector<vector<int>>;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
using vs = vector<string>;
using pii = pair<int, int>;
using mint = modint1000000007;
const int INF = 1e9;
const int MOD = 1e9 + 7;
const ll LINF = 1e18;
template <class T> bool chmax(T &a, const T &b) {if (a < b) {a = b;return 1;} return 0;}
template <class T> bool chmin(T &a, const T &b) {if (b < a) {a = b; return 1;} return 0;}

int main() {
    int n; cin >> n;
    vector<bool> isPrime(n + 1, true); isPrime[0] = isPrime[1] = false;
    reps(i, 2, n) {
        if (!isPrime[i]) continue;
        for (int j = 2 * i; j <= n; j+= i) {
            isPrime[j] = false;
        }
    }
    int count = 0;
    rep(i, n + 1) if (isPrime[i]) count++;

    vvi dp(count + 2, vi(n + 1));
    int index = 0;
    reps(i, 2, n + 1) {
        if (isPrime[i]) {
            index++;
            dp[index][i] = 1;
            reps(j, 2, n + 1) {
                chmax(dp[index][j], dp[index - 1][j]);
                if (i <= j && dp[index - 1][j - i] > 0) chmax(dp[index][j], dp[index - 1][j - i] + 1);
            }
        }
    }
    if (dp[count][n] > 0) cout << dp[count][n] << endl;
    else cout << -1 << endl;
    return 0;
}