#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define ll long long
#define pii pair<int, int>
#define soclose 1e-9
int N, K, M;
vector<pii> a;
vector<int> b;
bool f(int m) {
int day = 1;
for (int i = 0; i < M; ++i) {
b[i] = day;
if ((i + 1) % m == 0) day++;
}
for (int i = 0; i < M; ++i) {
if (a[i].first + K < b[i]) return false;
}
return true;
}
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
//freopen("angry.in", "r", stdin);
//freopen("angry.out", "w", stdout);
cin >> N >> K >> M;
a.resize(M);
for (int i = 0; i < M; ++i) {
cin >> a[i].first;
a[i].second = i + 1;
}
sort(all(a));
b.assign(M, 0);
int l = 0, r = M;
while (r - l > 1) {
int m = (l + r) / 2;
if (f(m)) r = m;
else l = m;
}
vector<int> ans[N];
int day = 0;
for (int i = 0; i < M; ++i) {
ans[day].push_back(a[i].second);
if ((i + 1) % r == 0) day++;
}
cout << r << '\n';
for (int i = 0; i < N; ++i) {
for (int x : ans[i]) cout << x << " ";
cout << "0\n";
}
return 0;
}
