#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdint>
using namespace std;
using Pair = pair<int64_t, int64_t>;
constexpr int64_t maxn = 1000000;
int64_t n, d, m;
Pair a[maxn];
int main()
{
ios_base::sync_with_stdio(false);
cin >> n >> d >> m;
for (int64_t i = 0; i < m; i++)
{
cin >> a[i].first;
a[i].second = i + 1;
}
sort(a, a + m);
int64_t l = ceil((float)m / (float)n), r = m;
while (l < r)
{
int64_t k = (l + r) / 2;
bool result = true;
for (int64_t i = 0; i * k < m; i++)
{
if (a[i * k].first + d <= i)
{
result = false;
break;
}
}
if (result)
r = k;
else
l = k + 1;
}
cout << l << '\n';
for (int64_t i = 0; i < n; i++)
{
for (int64_t j = i * l; j < min(m, (i + 1) * l); j++)
cout << a[j].second << ' ';
cout << "0\n";
}
return 0;
}
