#include <bits/stdc++.h>
using namespace std;
using ll = long long;



bool adhoc_comparator(const pair<string, ll> &a, const pair<string, ll> &b) {
    ll check_len = min(a.first.size(), b.first.size());
    for (ll i = 0; i < check_len; i++) {
        if (a.first[i] != b.first[i]) {
            return a.first[i] > b.first[i];
        }
    }
    if (a.first.size() < b.first.size()){
        return adhoc_comparator(a, {b.first.substr(check_len), b.second});
    }
    if (a.first.size() > b.first.size()){
        return adhoc_comparator({a.first.substr(check_len), a.second}, b);
    }
    else {
        return a.second > b.second;
    }
}

int main() {
    ll n, k;
    cin >> n >> k;
    vector<pair<string, ll>> v(n);
    for (ll i = 0; i < n; i++) {
        cin >> v[i].first;
        v[i].second = v[i].first.size();
    }
    sort(v.begin(), v.end(), adhoc_comparator);
    priority_queue<string> pq;
    for (ll i = 0; i < 800000; i++) {
        string s;
        for (ll j = 0; j < n; j++) {
            s += v[j].first;
        }
        pq.push(s);
        next_permutation(v.begin(), v.end(), adhoc_comparator);
    }
    string now = "z";
    for (ll i = 0; i < k; i++){
        while (now <= pq.top()){
            pq.pop();
        }
        cout << pq.top() << "\n";
        now = pq.top();
        pq.pop();
    }
    cout << flush;
}