#include <bits/stdc++.h>   using namespace std;   ifstream fin( Sisend.txt );   int n, c;   bool b[100005];   vector<int> v, v1;   int main() {     ios::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cerr.tie(0);     cin >> n;     for (int(i) = (0); ((i)) < ((n)); ((i))++) {       cin >> c;       v.emplace_back(c);     }     sort(v.rbegin(), v.rend());     int l = 1, r = v.size() / 2 + 1;     int vas = 0;     v1.emplace_back(v[0]);     while (r < v.size()) {       while (r < v.size() and v[r] == v[l]) r++;       v1.emplace_back(v[r]), v1.emplace_back(v[l]);       b[r] = 1;       vas++;       l++;       r++;     }     while (l < v.size()) {       if (!b[l]) {         v1.emplace_back(v[l]);       }       l++;     }     cout << vas << endl;     for (int i : v1) cout << i <<    ;   }   