#include <bits/stdc++.h>
using ll = long long;
using namespace std;
void debugi(vector<int>& vec) {
  int n = (int)vec.size();
  for (int i = 0; i < n; i++) {
    cout << vec[i] << " ";
  }
  cout << endl;
}
void debugl(vector<ll>& vec) {
  int n = (int)vec.size();
  for (int i = 0; i < n; i++) {
    cout << vec[i] << " ";
  }
  cout << endl;
}
void debugmap(map<int, int>& mp) {
  for (auto x : mp) {
    cout << x.first << " " << x.second << " , ";
  }
  cout << endl;
}
void debugset(set<int>& st) {
  for (auto x : st) {
    cout << x << " ";
  }
  cout << endl;
}
void debugparri(vector<pair<int, int>>& arr) {
  for (int i = 0; i < (int)arr.size(); i++) {
    cout << "[" << arr[i].first << " : " << arr[i].second << "]"
         << " ";
  }
  cout << endl;
}
void debugpi(pair<int, int>& pi) {
  cout << pi.first << " " << pi.second << endl;
}
void debugq(queue<int> q) {
  while (!q.empty()) {
    cout << q.front() << " ";
    q.pop();
  }
  cout << endl;
}
bool check(int n, int i, int j) {
  if ((0 <= i & i < n) && (0 <= j & j < n)) {
    return true;
  }
  return false;
}
ll mod = 998244353;
ll powab(ll a, ll b, ll mod) {
  if (b == 0) {
    return 1;
  }
  ll z = powab(a, b / 2, mod);
  ll res = (z * z * 1LL) % mod;
  if (b & 1) {
    res = (res * 1LL * a) % mod;
  }
  return res;
}
ll gcd(ll a, ll b) {
  if (b == 0) {
    return a;
  }
  return gcd(b, a % b);
}
void upd(int k, int x, vector<int>& tree, int n) {
  if (k == 0) {
    return;
  }
  while (k <= n) {
    tree[k] += x;
    k += (k & -k);
  }
}
int sum(int k, vector<int>& tree, int n) {
  int s = 0;
  while (k >= 1) {
    s += tree[k];
    k -= (k & -k);
  }
  return s;
}
int lim = -1;
int fi(vector<int>& arr, int l, int r, vector<int>& vis) {
  int low = 0, high = lim;
  int ans = -1;
  while (low <= high) {
    int mid = (low + high) / 2;
    if (arr[mid] < l && arr[mid] < r) {
      ans = mid;
      low = mid + 1;
    } else {
      high = mid - 1;
    }
  }
  if (ans == -1) {
    return -1;
  }
  vis[ans] = 1;
  lim = ans - 1;
  return arr[ans];
}
void solve(int t) {
  int n;
  cin >> n;
  vector<int> arr(n);
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr.begin(), arr.end());
  int i = 0, j = arr.size() - 1;
  vector<int> ans(n, -1);
  while (i < n) {
    ans[i] = arr[j];
    j -= 1;
    i += 2;
  }
  vector<int> l;
  for (int k = 0; k <= j; k++) {
    l.push_back(arr[k]);
  }
  vector<int> vis(l.size(), 0);
  int res = 0;
  lim = l.size() - 1;
  for (int i = 1; i < n; i += 2) {
    int l = -1, r = -1;
    l = ans[i - 1];
    if (i + 1 < n) {
      r = ans[i + 1];
    }
    if (r == -1) {
      continue;
    }
    int x = fi(arr, l, r, vis);
    if (x != -1) {
      res += 1;
      ans[i] = x;
    }
  }
  int a = 0;
  for (int i = 0; i < n; i++) {
    if (ans[i] == -1) {
      while (a < l.size()) {
        if (vis[a] == 0) {
          ans[i] = l[a];
          a += 1;
          break;
        }
        a += 1;
      }
    }
  }
  cout << res << endl;
  debugi(ans);
}
int main(int argc, const char* argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  t = 1;
  for (int tt = 0; tt < t; tt++) {
    solve(tt);
  }
  return 0;
}
