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

#define rep(i, a, b) for (auto i = a; i < (b); ++i)
#define repr(i, a, b) for (auto i = (a) - 1; i >= (b); --i)
#define pb push_back
#define eb emplace_back
#define all(x) begin(x), end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vii = vector<pii>;

template<class T>
inline bool cmax(T &a, const T& b) {
    return a < b ? a = b, 1 : 0;
}

template<class T>
inline bool cmin(T &a, const T &b) {
    return b < a ? a = b, 1 : 0;
}

const int inf = 0x3f3f3f3f;
const ll linf = 1e18;
const double dinf = numeric_limits<double>::infinity();

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int n, h;
    cin >> n >> h;
    unordered_map<int, int> cnt;
    for (int i = 0; i < n; i++) {
        int v;
        cin >> v;
        cnt[v]++;
    }

    int lo = 1, hi = n/h, res = 0, mid;
    while (lo <= hi) {
        mid = (lo+hi)/2;

        bool check = true;
        vi tmp;
        for (auto [key, value] : cnt) {
            for (int i = 0; i < min(value, mid); i++) {
                tmp.pb(key);
            }
        }

        check &= tmp.size() >= mid*h;

        if (check) {
            res = mid;
            lo = mid + 1;
        } else
            hi = mid - 1;
    }

    if (res == 0) cout << "impossible" << endl;
    else {
        vi tmp;
        for (auto [key, value] : cnt) {
            for (int i = 0; i < min(value, res); i++) {
                tmp.pb(key);
            }
        }
        
        for (int i = 0; i < res; i++) {
            for (int j = i; j < res*h; j += res) {
                cout << tmp[j] << " ";
            }
            cout << endl;
        }
    }

    return 0;
}