#include <bits/stdc++.h>
#include <cstdint>
using namespace std;
typedef long long ll;
typedef long double lld;
vector<string> s;
void solve(){
ll days,D,jobs_num;
cin>>days>>D>>jobs_num;
vector<vector<int>> jpd(days);
ll _max=-1;
vector<int> all_jobs;
for(int i=0;i<jobs_num;i++){
ll a;
cin>>a;
jpd[a-1].push_back(i+1);
_max=max(_max,(ll)jpd[a-1].size());
}
for(int i=0;i<jpd.size();i++){
all_jobs.push_back(jpd[i].size());
}
vector<vector<ll>> result(days);
auto check=[&](ll m,bool fill=false)->bool{
pair<int,int> curr_job={0,0};
int index=0;
for(int day=0;day<days;day++){
int _m=m;
while(_m && index<=day){
if(curr_job.second==0){
curr_job={index,all_jobs[index]};
index++;
}
ll can_do=min(_m,curr_job.second);
if(fill)
for(int i=curr_job.second-1;i>=curr_job.second-can_do;i--){
result[day].push_back(jpd[curr_job.first][i]);
}
_m-=can_do;
curr_job.second-=can_do;
if(day-curr_job.first>D){
return false;
}
}
}
return true;
};
ll hi=_max+1;
ll lo=0;
while(lo<hi){
ll mid=lo+(hi-lo)/2;
if(check(mid)){
hi=mid;
}else{
lo=mid+1;
}
}
check(hi,true);
cout<<hi<<endl;
for(auto i:result){
for(auto j:i){
cout<<j<<' ';
}
cout<<0<<" \n";
}
}
int main(){
solve();
}
