#include <bits/stdc++.h>
using namespace std;
bool check(int x, int n, vector<int>& a) {
  vector<int> temp;
  int i = 0, j = x;
  int cnt = 0;
  bool ok = false;
  while (cnt < n) {
    if (ok)
      temp.push_back(a[i]), i++, ok = false;
    else
      temp.push_back(a[j]), j++, ok = true;
    cnt++;
  }
  cnt = 0;
  return cnt == x;
}
void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a.begin(), a.end());
  int cnt = 0;
  vector<int> ans(n);
  for (int i = 1; i < n; i += 2) {
    ans[i] = a[cnt++];
  }
  for (int i = 0; i < n; i += 2) ans[i] = a[cnt++];
  cnt = 0;
  for (int i = 1; i < n - 1; i++) {
    if (ans[i] < ans[i - 1] && ans[i] < ans[i + 1]) cnt++;
  }
  cout << cnt << "\n";
  for (int i = 0; i < n; i++) cout << ans[i] << " ";
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ;
  int t = 1;
  while (t--) {
    solve();
    cout << "\n";
  }
  return 0;
}
