#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<algorithm>
#include<limits.h>
#include<math.h>
#include<map>
#include<set>
#include<unordered_map>
#include<unordered_set>
#include<iomanip>
#include<cstring>
#include<random>
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
using namespace std;
int n,d,m;
vector<int>jobs[100000];
vector<vector<int>>get(int k){
vector<vector<int>>res(n);
queue<pair<int,int>>q;
for(int i=0;i<n;i++){
for(int j:jobs[i]){
q.push({i+d,j});
}
if(q.size()&&q.front().first<i)
return {};
for(int j=0;j<k&&q.size();j++){
res[i].push_back(q.front().second);
q.pop();
}
}
return res;
}
void solve(){
cin>>n>>d>>m;
for(int i=1;i<=m;i++){
int a;
cin>>a;
jobs[a-1].push_back(i);
}
int l=0,r=m;
while(l<r-1){
int mid=(l+r)/2;
if(get(mid).empty()){
l=mid;
}else{
r=mid;
}
}
cout<<r<<"\n";
auto res=get(r);
for(auto i:res){
for(auto j:i){
cout<<j<<" ";
}
cout<<"0\n";
}
}
int main(){
ios::sync_with_stdio(false);cout.tie(NULL);cin.tie(NULL);
//freopen("/Users/jakob/cp_testing/test.txt","r",stdin);freopen("output.out","w",stdout);
int t=1;//cin>>t;
while(t--)solve();
return 0;
}
/*
8 2 12
1 2 4 2 1 3 5 6 2 3 6 4
*/
