#include<iostream>
#include<stdio.h>
#include<math.h>
#include<map>
#include<string>
#include<algorithm>
#include<vector>
#include<string.h>
#include<utility>
#include<set>
#include<cmath>
#include<queue>
#include<deque>
#include<functional>
#include<stack>
#include<limits.h>
#include<iomanip>
#include<unordered_map>
#include<numeric>
#include<tuple>
#include<bitset>
using namespace std;
#define MOD 1000000007
#define int long long
#define ss second
#define ff first
#define endl '\n'
signed main(){
// freopen("file.in", "r", stdin);
// freopen("file.out", "w", stdout);
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,d,m; cin>>n>>d>>m;
vector<int> v[n+1];
for(int i=1; i<=m; i++){
int a; cin>>a;
v[a].push_back(i);
}
int l=1,r=m;
while(l<=r){
int mid=l+(r-l)/2;
bool ok=1;
int sum=0;
for(int i=1; i<=n; i++){
sum+=v[i].size();
if((sum+mid-1)/mid-1>d) ok=0;
sum-=min(sum,mid);
}
if(ok) r=mid-1;
else l=mid+1;
}
queue<int> q;
cout<<l<<endl;
for(int i=1; i<=n; i++){
for(auto x: v[i]) q.push(x);
int need=l;
while(!q.empty()&&need--){
cout<<q.front()<<' ';
q.pop();
}
cout<<0<<endl;
}
return 0;
}
