#include <bits/stdc++.h>
using namespace std;
const int c = 1000005;
int n, pr[c];
unsigned long long ert[c], xo;
void co(vector<int> sz) {
  int si = sz.size();
  cout << n - si << "\n";
  for (int i = 1; i <= n; i++) {
    bool baj = 0;
    for (auto x : sz)
      if (x == i) baj = 1;
    if (!baj) cout << i << " ";
  }
  cout << "\n";
  exit(0);
}
void solve() {
  if (!xo) co({});
  map<unsigned long long, int> m;
  for (int i = 1; i <= n; i++) {
    if (xo == ert[i]) co({i});
    m[ert[i]] = i;
  }
  for (auto x : m) {
    unsigned long long p = xo ^ x.first;
    if (m.find(p) != m.end()) {
      co({x.second, m[p]});
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  mt19937_64 rng(
      (unsigned int)chrono::steady_clock::now().time_since_epoch().count());
  cin >> n;
  for (int i = 2; i <= n; i++) {
    if (!pr[i]) {
      ert[i] = rng();
      for (int j = i; j <= n; j += i) {
        pr[j] = i;
      }
    } else
      ert[i] = ert[i / pr[i]] ^ ert[pr[i]];
  }
  for (int i = 1; i <= n; i++) {
    ert[i] ^= ert[i - 1];
    xo ^= ert[i];
  }
  solve();
  xo ^= ert[n], n--;
  solve();
  return 0;
}
