#include <iostream>
    #include <vector>
    #include <fstream>
    #include <algorithm>
#include <cstring>
    using namespace std;
    int memo[10005];
    int n;
    vector<pair<pair<int, string>, vector<int> > > v;
int backtrack[10005];
    int dp(int index){
        if(index == n){
            return 0;
        }
        if(memo[index] != -1){
            return memo[index];
        }
        int res = 0;
        vector<int> a1;
        vector<int> b1;
        for (int i = index+1; i < v.size()  ; i++) {
            if(v[i].first.first == v[index].first.first + 1){
                bool ok = false;
                bool moze = true;
                a1 = v[i].second;
                b1 = v[index].second;
                for (int j = 0; j < 26; j++) {
                    if(a1[j] != b1[j] && ok == false){
                       if(abs(a1[j] - b1[j]) == 1){
                            ok = true;
                       }
                       else
                           moze = false;
                    }
                    else if(a1[j] != b1[j] && ok == true){
                        moze = false;
                        break;
                    }

                }
               if(moze){
                   if(res < dp(i) + 1) {
                       res = dp(i) + 1;
                       backtrack[index] = i;
                   }
               }
            }
        }
        return memo[index] = res;
    }

    int main()
    {

        cin >> n;
        memset(backtrack, -1, sizeof backtrack);
        for(int i = 0; i < n; i++) {
            string s;
            cin >> s;
            vector<int> cnt(26, 0);
            for(int j = 0; j < s.size(); j++) {
                cnt[s[j] - 'A']++;
            }
            v.push_back(make_pair(make_pair(s.size(), s), cnt));
        }
        sort(v.begin(), v.end());
        memset(memo, -1,sizeof memo);
        int result = 0, start_id = 0;

        for(int i =0 ; i < n; i++) {
            if(v[i].first.first == 2) {
                if(result < dp(i)) {
                    result = dp(i) + 1;
                    start_id = i;
                }
            }
        }
//        cout << result << endl;
        if(result <= 1) {
            cout << 1 << "\n";
            cout << "A" << endl;
            return 0;
        }
        vector<string> ans;
        ans.push_back(string() + v[start_id].first.second[0]);

        int A = start_id;
        while(A != -1) {
            ans.push_back(v[A].first.second);
            A = backtrack[A];
        }
        if(ans[0].size() == ans[1].size()) {
            ans.erase(ans.begin());
        }
        cout << ans.size() << "\n";
        for(int i = 0; i < ans.size(); i++) {
            cout << ans[i] << "\n";
        }
        return 0;
    }