import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Scanner;
import java.util.ArrayList;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author silviase
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        DifferentSumOfPrime solver = new DifferentSumOfPrime();
        solver.solve(1, in, out);
        out.close();
    }

    static class DifferentSumOfPrime {
        public void solve(int testNumber, Scanner in, PrintWriter out) {

            // 2万なのでN^2くらいは通りそうだけど…
            int n = in.nextInt();
            ArrayList<Integer> primes = Prime.eratosthenes(n);
            int[] dp = new int[n + 1];
            // dp[i] = i を異なる素数の和で表した時の最大個数
            Arrays.fill(dp, -1);

            for (Integer p : primes) {
                for (int i = n; i > p; i--) {
                    if (dp[i - p] > 0) {
                        dp[i] = Math.max(dp[i], dp[i - p] + 1);
                    }
                }
                dp[p] = Math.max(dp[p], 1);
                // out.println(Arrays.toString(dp));
            }

            out.println(dp[n]);
        }

    }

    static class Prime {
        public static ArrayList<Integer> eratosthenes(int n) {
            // n以下の素数をすべて列挙する(計算量は O(N log(log N)))
            // ただし10^5が耐用限界っぽい感じはする

            ArrayList<Integer> res = new ArrayList<>();
            ArrayList<Integer> primes = new ArrayList<>();
            for (int i = 2; i <= n; i++) {
                res.add(i);
            }
            while (res.size() > 0) {
                primes.add(res.get(0));
                res.removeIf(a -> a % res.get(0) == 0);
            }
            return primes;
        }

    }
}