#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
long long mod(long long x) { return ((x % MOD + MOD) % MOD); }
long long add(long long a, long long b) { return mod(mod(a) + mod(b)); }
long long mul(long long a, long long b) { return mod(mod(a) * mod(b)); }
void solve() {
  long long n, k;
  cin >> n >> k;
  long long a[k];
  long long visited[n * k + 2];
  memset(visited, 0, sizeof(visited));
  for (long long i = 0; i < k; i++) {
    cin >> a[i];
    visited[a[i]] = 1;
  }
  for (long long i = 0; i < k; i++) {
    cout << a[i] << " ";
    long long cnt = 1, j = 1;
    while (cnt < n) {
      if (visited[j] == 0) {
        cout << j << " ";
        visited[j] = 1;
        j++;
        cnt++;
      } else
        j++;
    }
    cout << endl;
  }
}
signed main() {
  long long t = 1;
  while (t--) {
    solve();
  }
}
