#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cassert>
#include <algorithm>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <map>
#include <set>

using namespace std;

#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#define pb push_back
#define mp make_pair
#define sz(x) ((int)(x).size())

typedef long long ll;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef pair<int, int> pii;

const int MAXN = 1e5 + 1e3;
const int MAXM = 1e6 + 1e3;

int n, d, m;
int firs[MAXN];
int nes[MAXM];

int ids[MAXN];
int nes2[MAXM];

bool check(int maxw, bool write = false) {
  if (write) {
    memset(firs, -1, sizeof firs);
  }

  int ptr = 0, csz = 0;
  for (int cst = 0; cst < n; cst++)
  for (int i = ids[cst]; i >= 0; i = nes2[i]) {
    while (ptr < cst) { ptr++; csz = 0; }
    if (csz >= maxw) { ptr++; csz = 0; }

    if (ptr >= n || ptr > cst + d) return false;
    csz++;
    if (write) {
      nes[i] = firs[ptr];
      firs[ptr] = i;
    }
  }
  return true;
}

int main() {
  #ifdef DEBUG
  freopen("std.in", "r", stdin);
  freopen("std.out", "w", stdout);
  #endif

  while (scanf("%d%d%d", &n, &d, &m) >= 1) {
    memset(ids, -1, sizeof ids);
    for (int i = 0; i < m; i++) {
      int x;
      scanf("%d", &x), x--;
      nes2[i] = ids[x];
      ids[x] = i;
    }

    int L = 0, R = m;
    assert(check(R));
    while (L + 1 < R) {
      int M = (L + R) / 2;
      if (check(M)) R = M;
      else L = M;
    }
    printf("%d\n", R);

    check(R, true);
    for (int i = 0; i < n; i++) {
      for (int i2 = firs[i]; i2 >= 0; i2 = nes[i2])
        printf("%d ", i2 + 1);
      printf("0\n");
    }

    #ifndef DEBUG
    break;
    #endif
  }
  return 0;
}