#include <bits/stdc++.h>
using namespace std;
using namespace chrono;
template <class T>
inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <typename Arg1>
void __f(const char *name, Arg1 &&arg1) {
  cerr << name << " : " << arg1 << std::endl;
}
template <typename Arg1, typename... Args>
void __f(const char *names, Arg1 &&arg1, Args &&...args) {
  const char *comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << " : " << arg1 << " | ";
  __f(comma + 1, args...);
}
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '\"' << x << '\"'; }
void __print(const string &x) { cerr << '\"' << x << '\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
const long long int inf = 2e18;
const long long int mod = 1e9 + 7;
const long long int N = 1e6 + 3;
int main() {
  auto start_time = high_resolution_clock::now();
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n;
  cin >> n;
  vector<long long int> v(n), ar(n, -1);
  for (auto i = 0ll; i < n; ++i) cin >> v[i];
  sort((v).begin(), (v).end(), greater<long long int>());
  for (long long int i = 1; i < n; i += 2) {
    ar[i] = v.back();
    v.pop_back();
  }
  for (long long int i = 0; i < n; i += 2) {
    ar[i] = v.back();
    v.pop_back();
  }
  long long int cnt = 0;
  for (long long int i = 1; i < n - 1; ++i) {
    if (ar[i - 1] > ar[i] && ar[i] < ar[i + 1]) ++cnt;
  }
  cout << cnt << "\n";
  for (auto i : ar) {
    cout << i << " ";
  }
  auto end_time = high_resolution_clock::now();
  return 0;
  cout << "\nTime elapsed: "
       << (double)duration_cast<milliseconds>(end_time - start_time).count()
       << "ms";
  return 0;
}
