#include <bits/stdc++.h>
using namespace std;
bool czy (int n, int d, vector<int> &v, vector<int> &sp, int k) {
int dost = 0, wyk = 0;
for (int i = 1; i <= n; i++) {
dost += v[i];
wyk = min(dost, wyk+k);
if (dost > wyk+d*k) {
return 0;
}
}
return 1;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, d, m;
cin >> n >> d >> m;
vector<int> v (n+1, 0), sp (n+1, 0);
vector<vector<int>> c (n+1);
for (int i = 1; i < m+1; i++) {
int x;
cin >> x;
v[x]++;
c[x].push_back(i);
}
for (int i = 1; i <= n; i++) {
sp[i] = sp[i-1]+v[i];
}
int k = 0;
int p = 1<<29;
while (p > 0) {
k += p;
if (czy(n, d, v, sp, k)) {
k -= p;
}
p /= 2;
}
//k++;
cout << k << '\n';
queue<int> q;
for (int i = 1; i <= n; i++) {
for (int j : c[i]) {
q.push(j);
}
for (int j = 0; j < k; j++) {
if (q.empty()) {
break;
}
cout << q.front() << ' ';
q.pop();
}
cout << "0\n";
}
}
