#include <bits/stdc++.h>
using namespace std;
int n, D, M;
vector<pair<int, int>> vec;
vector<vector<int>> ansDetail;
bool chk(int mid)
{
int ptr = 0;
for (int day = 1; day <= n; day++)
{
ansDetail[day].clear();
if (ptr >= M)
continue;
for (int i = 1; i <= mid and ptr < M; i++)
{
if (day > vec[ptr].first + D)
return false;
if (day >= vec[ptr].first)
{
ansDetail[day].emplace_back(vec[ptr].second);
ptr++;
}
if (ptr >= M or day < vec[ptr].first)
{
break;
}
}
}
return true;
}
int main()
{
cin.tie(0)->sync_with_stdio(0);
cin >> n >> D >> M;
ansDetail.resize(n + 1);
for (int i = 1; i <= M; i++)
{
int x;
cin >> x;
vec.emplace_back(x, i);
}
sort(vec.begin(), vec.end());
int l = 1, r = M, ans = -1;
while (l <= r)
{
int mid = (l + r) >> 1;
if (chk(mid))
{
ans = mid;
r = mid - 1;
}
else
{
l = mid + 1;
}
}
cout << ans << "\n";
for (int i = 1; i <= n; i++)
{
for (int v : ansDetail[i])
{
cout << v << " ";
}
cout << "0\n";
}
}
