#include <bits/stdc++.h>
using namespace std;
int N, M, D;
const int maxm = 1000010;
const int maxn = 100010;
vector<int> ac[maxn]; //store indices of all that start at me
int ans[maxm];
int st[maxm]; //store start for all values
vector<int> res[maxn];
bool go(int mid) {
queue<int> q;
for (int i = 1; i <= N; i++) {
for (int v : ac[i]) q.push(v);
for (int j = 1; j <= mid; j++) {
if (q.empty()) break;
if (st[q.front()] + D < i) return false;
ans[q.front()] = i;
q.pop();
}
}
return q.size() == 0;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> N >> D >> M;
int cur;
for (int i = 1; i <= M; i++) {
cin >> cur;
st[i] = cur;
ac[cur].push_back(i);
}
int lo = 1;
int hi = M;
while (lo < hi) {
int mid = (lo + hi)/2;
if (go(mid)) {
hi = mid;
}
else lo = mid+1;
}
go(lo);
for (int i = 1; i <= M; i++) {
res[ans[i]].push_back(i);
}
cout << lo << endl;
for (int i = 1; i <= N; i++) {
for (int v : res[i]) cout << v << " ";
cout << 0 << '\n';
}
cout.flush();
}
