#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
int knigtx8[] = {2, 2, -2, -2, 1, 1, -1, -1};
int knigty8[] = {1, -1, 1, -1, 2, -2, 2, -2};
int dx8[] = {0, 0, 1, 1, 1, -1, -1, -1};
int dy8[] = {1, -1, 1, -1, 0, 0, -1, 1};
int dx4[] = {0, 0, 1, -1};
int dy4[] = {1, -1, 0, 0};
const int maxx = 100005;
bool sortinrev(const pair<int, int> &a, const pair<int, int> &b) {
  return a.first > b.first;
}
long long pw(long long a, long long b) {
  long long ans = 1;
  for (long long i = 1; i <= b; ++i) ans = (ans * a);
  return ans;
}
template <typename T>
inline T Bigmod(T base, T power, T MOD) {
  T ret = 1;
  while (power) {
    if (power & 1) ret = (ret * base) % MOD;
    base = (base * base) % MOD;
    power >>= 1;
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<long long> v(n), u(n, 0);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  if (n <= 2) {
    cout << 0 << endl;
    for (auto i : v) cout << i << " ";
    return 0;
  }
  long long cnt = 0;
  sort(v.begin(), v.end());
  for (int i = 0; i < n; i++) {
    if (i & 1) u[i] = v[cnt++];
  }
  for (long long i = n - 1; i >= 0; i--) {
    if (i % 2 == 0) u[i] = v[cnt++];
  }
  long long ans = 0;
  for (int i = 1; i <= n - 1; i++) {
    if (u[i - 1] > u[i] and u[i + 1] > u[i]) ans++;
  }
  cout << ans << endl;
  for (auto i : u) cout << i << " ";
}
