#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <set>
#include <cstdlib>

using namespace std;

int n, K;
string a[100];

bool cmp(string x, string y) {
    if (x + y != y + x) return x + y > y + x;
    return x.size() > y.size();
}

int main() {
    cin >> n >> K;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(a, a + n, cmp);
    vector<string> ans;
    for (int ii = 0; ii < 100000; ii++) {
        for (int i = 0; i + 1 < n; i++) {
            if (a[i] + a[i + 1] == a[i + 1] + a[i] && a[i] < a[i + 1]) {
                swap(a[i], a[i + 1]);
            }
        }
        string s;
        for (int i = 0; i < n; i++) {
            s += a[i];
        }
        ans.push_back(s);
        next_permutation(a, a + n, cmp);
    }
    sort(ans.rbegin(), ans.rend());
    ans.erase(unique(ans.begin(), ans.end()), ans.end());
    for (int i = 0; i < K; i++) {
        cout << ans[i] << endl;
    }
}