#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
#include <unordered_map>
#include <unordered_set>
#define ll long long
#define ld long double
#define pl pair<ll, ll>
#define vi vector<ll>
#define vii vector<vi>
#define vc vector<char>
#define vcc vector<vc>
#define vp vector<pl>
#define mi map<ll,ll>
#define mc map<char,int>
#define sortx(X) sort(X.begin(),X.end());
#define all(X) X.begin(),X.end()
#define allr(X) X.rbegin(),X.rend()
#define ln '\n'
#define YES {cout << "YES\n"; return;}
#define NO {cout << "NO\n"; return;}
#define MUN {cout << "-1\n"; return;}
const int MODE = 1e9 + 7;
using namespace std;
const int MX = 1e5 + 1;
void solve(int tc) {
ll n, k, m;
cin >> n >> k >> m;
vii X(n + 1);
for (int i = 0; i < m; i++) {
ll a; cin >> a; X[a].push_back(i + 1);
}
ll l = 1, r = m;
while (l < r)
{
ll mid = (l + r) / 2;
deque<ll> dq;
bool isit = 1;
for (int i = 1; i <= n; i++)
{
for (int j = 0; j < X[i].size(); j++)
dq.push_back(i + k);
for (int j = 0; j < mid && !dq.empty(); j++)
dq.pop_front();
if (!dq.empty() && dq.front() <= i) isit = 0;
}
if (isit) r = mid - 1;
else l = mid + 1;
}
cout << l << '\n';
queue<ll> q;
for (int i = 1; i <= n; i++)
{
for (int j = 0; j < X[i].size(); j++) q.push(X[i][j]);
for (int j = 0; j < l && !q.empty(); j++)
{
cout << q.front() << ' ';
q.pop();
}
cout << "0\n";
}
}
int main()
{
ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
int size = 1;
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
// cin >> size;
for (int i = 1; i <= size; i++)
solve(i);
}
