#include <bits/stdc++.h>   using namespace std;   void fastio() {     cin.tie(nullptr);     cin.sync_with_stdio(false);   }   using LL = long long;   using LD = long double;   const LL MOD = 1e9 + 7;   const LL INF = LLONG_MAX;   const LL N = 2e5 + 1;   int main() {     fastio();     LL n;     cin >> n;     vector<LL> a(n);     for (auto &e : a) {       cin >> e;     }     vector<LL> ans(n, 0);     sort(a.begin(), a.end(), greater<LL>());     LL p = 0;     for (LL i = 0; i < n; i += 2) {       ans[i] = a[p++];     }     for (LL i = 0; i < n; ++i) {       if (ans[i] == 0) {         ans[i] = a[p++];       }     }     cout << (n - 1) / 2 <<   n ;     for (auto &e : ans) {       cout << e <<    ;     }     cout <<   n ;   }   