#include <bits/stdc++.h>
#define int int64_t
//GCC optimize ("O3");

using namespace std;
typedef long long ll;
typedef pair <string, string> pss;
typedef vector <pss> vpss;
int n, m;
vpss v;
map <string, int> cnt;
map <string, int> cnt1;

int32_t main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    cin >> n >> m;
    for (int i = 0; i < n; i++)
    {
        string s;
        cin >> s;
        int j = 0;
        while (s [j] != '.' && j < s.size())
            j++;
        pss p;
        if (j != s.size())
        {
            p.first = s.substr(0, j);
            p.second = s.substr(j, s.size());
        }
        else
        {
            p.first = s;
            p.second = "";
        }
        cnt [p.first] ++;
        cnt1 [p.second] ++;
        v.push_back(p);
    }
    if (cnt1 [""] > 0 && cnt1 ["."] > 0)
    {
        cnt1 [""] += cnt1 ["."];
        cnt1 ["."] = cnt1 [""];
    }
    map <string, bool> m1;
    map <string, bool> m2;
    m++;
    while (m > 1)
    {
        for (int i = 0; i < v.size(); i++)
        {
            if (cnt1 [v [i].second] == 1 && m1 [v [i].first] == 0 && m2 [v [i].second] == 0 && cnt [v [i].first] > 0)
            {
                cnt [v [i].first] --;
                if (v [i].second == "" || v [i].second == ".")
                {
                    cnt1 [""]--;
                    cnt1 ["."]--;
                }
                else
                    cnt1 [v [i].second] --;
                m2 [v [i].second] = 1;
                continue;
            }
        }
        m--;
        if (m > 1)
        {
            for (int i = 0; i < v.size(); i++)
            {
                if (cnt [v [i].first] == 1 && m1 [v [i].first] == 0 && m2 [v [i].second] == 0 && cnt1 [v [i].second] > 0)
                {
                    cnt [v [i].first] --;
                    if (v [i].second == "" || v [i].second == ".")
                    {
                        cnt1 [""]--;
                        cnt1 ["."]--;
                    }
                    else
                        cnt1 [v [i].second] --;
                    m1 [v [i].first] = 1;
                    continue;
                }
            }
        }
        m1.clear();
        m2.clear();
        m--;
    }
    vector <string> ans;
    for (int i = 0; i < v.size(); i++)
    {
        if (cnt [v [i].first ] > 0 && cnt1 [v [i].second ] > 0)
            ans.push_back(v [i].first + v [i].second);
    }
    cout << ans.size() << "\n";
    for (int i = 0;i < ans.size(); i++)
        cout << ans [i] << "\n";
}