#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int n, m;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  int b[n], c[n];
  if (n % 2 == 0)
    m = n - 3;
  else if (n % 2 != 0)
    m = n - 2;
  int p = n - 1;
  for (int i = 0; i < n; i += 2) {
    b[i] = a[p];
    c[i] = a[p];
    p--;
  }
  int k = 0, sum1 = 0;
  for (int i = m; i >= 0; i -= 2) {
    b[i] = a[k];
    k++;
  }
  if (m == n - 3) b[n - 1] = a[k];
  for (int i = 1; i < n - 1; i++) {
    if (b[i] < b[i - 1] && b[i] < b[i + 1]) sum1++;
  }
  k = 0;
  int sum2 = 0;
  for (int i = 1; i < n; i += 2) {
    c[i] = a[k];
    k++;
  }
  for (int i = 1; i < n - 1; i++) {
    if (c[i] < c[i - 1] && c[i] < c[i + 1]) sum2++;
  }
  if (sum1 > sum2) {
    cout << sum1 << endl;
    for (int i = 0; i < n; i++) {
      cout << b[i] << " ";
    }
    cout << endl;
  } else {
    cout << sum2 << endl;
    for (int i = 0; i < n; i++) {
      cout << c[i] << " ";
    }
  }
}
