#include <iostream>
#include <cmath>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <unordered_map>
#include <queue>
#include <deque>
#include <set>
#include <unordered_set>
#include <complex>
#include <list>
#include <cassert>
#include <chrono>
#include <random>
#include <stack>
#include <iomanip>
#include <fstream>
using namespace std;
#define endl "\n"
// #define int long long
const int INF = 1e9+7;
const int MOD = 1e9+7;
const int MAXN = 1e6+5;
int days, delay, n;
bool check(int m, vector<pair<int, int>> &a){
vector<int> cnt(MAXN, 0);
for(int i = 0; i < n; i+=m){
cnt[a[i].first]++;
}
for(auto &i : cnt){
if(i > delay) return false;
}
return true;
}
void solve(){
cin >> days >> delay >> n;
vector<pair<int, int>> a(n);
for(int i = 0; i < n; i++) { cin >> a[i].first; a[i].second = i+1; }
sort(a.begin(), a.end());
int l = 1, r = INF, sol = 0;
while(l <= r){
int m = (l+r)/2;
if(check(m, a)){
sol = m;
r = m-1;
} else {
l = m+1;
}
}
cout << sol << endl;
int prevj = 0;
for(int i = 0; i < days; i++){
int j = prevj;
for(; j < min(n, prevj+sol); j++){
cout << a[j].second << " ";
}
prevj = j;
cout << 0 << endl;
}
}
int32_t main(){
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int t = 1;
// cin >> t;
while(t--) solve();
return 0;
}
