/*
* Author: bubu2006
**/
#include <bits/stdc++.h>
using namespace std;
int n, d, m;
vector<pair<int, int>> req;
pair<bool, vector<vector<int>>> ok(int x) {
vector<vector<int>> res(n);
int aint = 0;
for(int day = 1; day <= n; day++) {
for(int j = 0; j < x; j++) {
if(req[aint].first > day) {
break;
}
if(req[aint].first + d >= day) {
res[day - 1].push_back(req[aint++].second);
} else {
return {0, res};
}
if(aint == m) {
return {1, res};
}
}
}
return {0, res};
}
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> d >> m;
req.resize(m);
for(int i = 0; i < m; i++) {
cin >> req[i].first;
req[i].second = i + 1;
}
sort(req.begin(), req.end());
vector<vector<int>> ans;
int l = 0;
int r = m;
while(l < r - 1) {
int mid = l + (r - l) / 2;
auto tmp = ok(mid);
if(tmp.first) {
r = mid;
ans = tmp.second;
} else {
l = mid;
}
}
cout << r << '\n';
for(int i = 0; i < n; i++) {
for(int j : ans[i]) {
cout << j << ' ';
}
cout << 0 << '\n';
}
}
