#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 5;
int n, d, m;
int a[MAXN];
vector<int> peal[100005];
vector<int> res[MAXN];
bool ck(int x)
{
int cnt = 0;
int j = 1;
for (int i = 1; i <= n - d; i++)
{
int k = 0;
if (j < i)
{
j = i;
cnt = 0;
}
while(k < peal[i].size() and j <= n and j <= i + d)
{
cnt++;
k++;
if (cnt == x)
{
cnt = 0;
j++;
}
}
if (k < peal[i].size())
{
return false;
}
}
return true;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> d >> m;
for (int i = 1; i <= m; i++)
{
cin >> a[i];
peal[a[i]].push_back(i);
}
int l = 1;
int r = m;
int ans = -1;
while(l <= r)
{
int mid = (l + r) / 2;
if (ck(mid))
{
ans = mid;
r = mid - 1;
}
else
{
l = mid + 1;
}
}
cout << ans << "\n";
int j = 1;
for (int i = 1; i <= n - d; i++)
{
int k = 0;
j = max(j, i);
while(k < peal[i].size() and j <= n and j <= i + d)
{
res[j].push_back(peal[i][k]);
k++;
if (res[j].size() == ans)
{
j++;
}
}
}
for (int i = 1; i <= n; i++)
{
for (auto v : res[i])
{
cout << v << " ";
}
cout << 0 << "\n";
}
}
