#include <bits/stdc++.h>
using namespace std;
int Set(int N, int pos) { return N = N | (1 << pos); }
int reset(int N, int pos) { return N = N & ~(1 << pos); }
bool check(int N, int pos) { return (bool)(N & (1 << pos)); }
int cas = 1;
int dxx[] = {-1, -1, -1, 0, 0, 1, 1, 1};
int dyy[] = {-1, 0, 1, -1, 1, -1, 0, 1};
int dx[] = {-1, 0, 0, 1};
int dy[] = {0, -1, 1, 0};
int main() {
  int n;
  scanf("%d", &n);
  if (n % 2 == 0) {
    cout << n / 2 << endl;
    for (int i = 1; i <= n / 2; i++) {
      printf("2 ");
    }
    cout << endl;
  } else {
    cout << (n - 3) / 2 + 1 << endl;
    for (int i = 1; i <= (n - 3) / 2; i++) {
      printf("2 ");
    }
    printf(" 3");
  }
  return 0;
}
