#include <bits/stdc++.h>   using namespace std;   const int maxn = 1e6 + 5;   string s[10005];   int vis[10005];   int main() {     ios::sync_with_stdio(0);     int n, sum(0);     cin >> n;     for (long long i = 0; i < n; ++i) cin >> s[i], sum += s[i].size();     char c;     cin >> c;     for (long long i = 0; i < n; ++i) s[i] += c;     sort(s, s + n);     sum = sum * 2 / n + 1;     for (long long i = 0; i < n; ++i)       if (!vis[i]) {         cout << s[i];         vis[i]++;         for (long long j = i + 1; j < n; ++j)           if (!vis[j] && sum - s[i].size() == s[j].size() - 1) {             cout << s[j].substr(0, s[j].size() - 1) <<   n ;             vis[j]++;             break;           }       }   }   