#include <bits/stdc++.h>
using namespace std;
long long int M = 1e9 + 7;
long long int M2 = 998244353;
long long int M3 = 1e8;
long long int MAX = 5001;
string s = "Everything correct till here!";
void show(vector<long long int> v) {
  for (long long int i = 0; i < v.size(); i++) cout << v[i] << " ";
  cout << "\n";
}
void showrev(vector<long long int> v) {
  for (long long int i = 0; i < v.size(); i++)
    cout << v[v.size() - i - 1] << " ";
  cout << "\n";
}
void showarr(long long int arr[], long long int n) {
  for (long long int i = 0; i < n; i++) cout << arr[i] << " ";
  cout << "\n";
}
void showpv(vector<pair<long long int, long long int> > v) {
  for (long long int i = 0; i < v.size(); i++)
    cout << v[i].first << " " << v[i].second << "\n";
}
void solve() {
  long long int n;
  cin >> n;
  long long int a[n];
  for (long long int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  if (n <= 2) {
    cout << "0\n";
    showarr(a, n);
    return;
  }
  long long int dp[n];
  long long int k = 1;
  for (long long int i = 0; i < n; i++) {
    dp[k] = a[i];
    k += 2;
    if (k > n - 1) k = 0;
  }
  cout << (n - 1) / 2 << "\n";
  showarr(dp, n);
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long int T = 1, Q = 1;
  while (T--) {
    solve();
  }
  return 0;
}
