#include <bits/stdc++.h>
using namespace std;
int n, d, m;
deque<pair<int,int>> dq;
vector<vector<int>> res;
bool check(int x) {
res.assign(n + 1, vector<int>());
int p = 0;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= x; j++) {
int t = dq[p].first;
if (t > i) break;
if (t + d >= i) {
res[i].push_back(dq[p].second);
p++;
}
else return false;
if (p == m) return true;
}
}
return false;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n >> d >> m;
dq.resize(m);
for (int i = 0; i < m; i++) {
cin >> dq[i].first;
dq[i].second = i + 1;
}
sort(dq.begin(), dq.end());
int l = 1, r = m, ans = -1;
vector<vector<int>> sav;
while (l <= r) {
int x = (l + r) / 2;
if (check(x)) {
ans = x;
sav = res;
r = x - 1;
}
else l = x + 1;
}
cout << ans << '\n';
for (int i = 1; i <= n; i++) {
for (auto &j : sav[i]) cout << j << ' ';
cout << 0 << '\n';
}
}
