#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  cout << (n - 1) / 2 << endl;
  vector<int> v(n);
  int j = 0;
  for (int i = 1; i < n; i += 2, j++) {
    v[i] = a[j];
  }
  for (int i = 0; i < n; i += 2, j++) {
    v[i] = a[j];
  }
  for (int i = 0; i < n; i++) cout << v[i] << " ";
  return 0;
}
