import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Primes {
    private void solve() throws IOException {
        int n = readInt();
        out.println(n / 2);
        while (n > 3) {
            out.print(2 + " ");
            n -= 2;
        }
        out.println(n);
    }

//------------------------------------------------------------------------------
    public static void main(String[] args) {
        new Primes().run();
    }

    private void run() {
        try {
            initIO();
            solve();
            in.close();
            out.close();
        } catch (Throwable e) {
            throw new RuntimeException(e);
        }
    }

    private BufferedReader in;
    private StringTokenizer tok;
    private PrintWriter out;

    private void initIO() throws IOException {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
//        in = new BufferedReader(new FileReader(new File("input.txt")));
//        out = new PrintWriter(new File("output.txt"));
    }

    private String readString() throws IOException {
        while (tok == null || !tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine());
        }
        return tok.nextToken();
    }

    @SuppressWarnings("unused")
    private int readInt() throws IOException {
        return Integer.parseInt(readString());
    }

    @SuppressWarnings("unused")
    private long readLong() throws IOException {
        return Integer.parseInt(readString());
    }

    @SuppressWarnings("unused")
    private double readDouble() throws IOException {
        return Double.parseDouble(readString());
    }
}