#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define str string
#define vi vector<int>
#define vll vector<long long>
#define vc vector<char>
#define vs vector<string>
#define pi pair<int, int>
#define vpi vector<pi>
#define vvi vector<vector<int>>
#define si set<int>
#define ins insert
#define pb(a) push_back(a)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, b) for (int i = 0; i < (b); i++)
#define fast_io \
ios_base::sync_with_stdio(false); \
std::cin.tie(NULL)
#define coutyes cout << "YES" << endl;
#define coutno cout << "NO" << endl;
using namespace std;
ll n, d, m;
vvi vv(n);
bool good(vector<pair<int, int>> &v, int mid)
{
vector<vi> schedule(n);
int reqNum = 0;
for (int day = 1; day <= n; day++)
{
for (int j = 0; j < mid; j++)
{
if (v[reqNum].first > day)
{
break;
}
if (v[reqNum].first + d >= day)
{
schedule[day - 1].push_back(v[reqNum++].second);
}
else
{
return false;
}
if (reqNum == m)
{
vv = schedule;
return true;
}
}
}
return false;
}
void solve()
{
cin >> n >> d >> m;
vpi v(m);
for (int i = 0; i < m; i++)
{
cin >> v[i].first;
v[i].second = i + 1;
}
sort(all(v));
int lo = 1, hi = m, ans = hi;
while (hi >= lo)
{
int mid = lo + (hi - lo) / 2;
if (good(v, mid))
{
ans = mid;
hi = mid - 1;
}
else
lo = mid + 1;
}
cout << ans << '\n';
for (int i = 0; i < n; i++)
{
for (int j = 0; j < vv[i].size(); j++)
{
cout << vv[i][j] << ' ';
}
cout << 0 << '\n';
}
}
int main()
{
fast_io;
ll t;
// cin >> t;
t = 1;
while (t--)
{
solve();
}
return 0;
}
