#include <bits/stdc++.h>
using namespace std;
vector<vector<int>> ans(100001);
bool ok(int machines, vector<pair<int, int>>& t, int m, int d, int n) {
for (int i = 1; i <= n; i++) {
ans[i].clear();
}
// need to check if all tasks can be done at most D days after scheduled
int req = 0;
for (int day = 1; day <= n; day++) {
for (int j = 0; j < machines; j++) {
if (req == m) {
return true;
}
if (t[req].first > day) {
break;
}
if (day > t[req].first+d) {
return false;
}
ans[day].push_back(t[req++].second);
}
}
return true;
}
int main() {
int n, d, m;
cin >> n >> d >> m;
vector<pair<int, int>> t(m);
for (int i = 0; i < m; i++) {
cin >> t[i].first;
t[i].second = i+1;
}
sort(t.begin(), t.end());
int lo = 1;
int hi = m;
while (lo < hi) {
int mid = (lo+hi)/2;
if (ok(mid, t, m, d, n)) {
hi = mid;
} else {
lo = mid+1;
}
}
cout << lo << endl;
ok(lo, t, m, d, n);
for (int i = 1; i <= n; i++) {
for (int task : ans[i]) {
cout << task << " ";
}
cout << 0 << endl;
}
return 0;
}
