#include <bits/stdc++.h>
using namespace std;
template <class T1, class T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << "{" << p.first << "," << p.second << "}";
  return os;
}
const int N = 2e6 + 5;
const int oo = 1e9 + 7;
int lp[N + 1];
vector<int> pr;
void sieve() {
  for (int i = 2; i <= N; ++i) {
    if (lp[i] == 0) {
      lp[i] = i;
      pr.push_back(i);
    }
    for (int j = 0; j < (int)pr.size() && pr[j] <= lp[i] && i * pr[j] <= N; ++j)
      lp[i * pr[j]] = pr[j];
  }
}
int n;
int a[N];
bool isp[N];
int cnt(int x) { return upper_bound(a, a + n, x) - lower_bound(a, a + n, x); }
int chk() {
  for (int i = upper_bound(a, a + n, 1) - a; i < n; i++) {
    if (isp[a[i] + 1]) return a[i];
  }
  return 0;
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  sieve();
  for (int i : pr) isp[i] = 1;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  int y = chk();
  int x = cnt(1) + (y > 0);
  if (x >= 2) {
    cout << x << "\n";
    if (y) {
      cout << y << " ";
      x--;
    }
    for (int i = 1; i <= x; i++) cout << "1 ";
    cout << "\n";
  } else {
    for (int i = 0; i < n; i++) {
      for (int j = i + 1; j < n; j++) {
        if (isp[a[i] + a[j]]) {
          cout << "2\n";
          cout << a[i] << " " << a[j] << endl;
          return 0;
        }
      }
    }
    cout << "1\n";
    cout << a[0] << "\n";
  }
}
