#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define endl "\n"
long long a,b,c,d,e,f,m,n,h,l,r,k,x,y,ans,sum;
// bool sortcol(const vector<int>& v1, const vector<int>& v2){
// return v1[1] < v2[1];
// }
int C, D, K, N, M;
pair<bool, vector<vector<int>>> bin_search(int mid, vector<pair<int, int>> &A){
vector<vector<int>>B(N);
int idx = 0;
for(int day = 1; day <= N; day++){
for(int j = 0; j < mid; j++){
if(A[idx].first > day){
break;
}
if(A[idx].first + D >= day){
B[day - 1].push_back(A[idx].second);
idx++;
}
else return {false, B};
if(idx == M){
return {true, B};
}
}
}
return {false, B};
}
int32_t main(){
// freopen("angry.in", "r", stdin);
// freopen("angry.out", "w", stdout);
cin>>N>>D>>M;
vector<pair<int, int>>A;
for(int i = 0; i < M; i++){
cin>>a;
A.push_back({a, i + 1});
}
sort(A.begin(), A.end());
vector<vector<int>>res;
int left = 0, right = M;
while(left < right){
int mid = left + ((right - left) / 2);
pair<bool, vector<vector<int>>> answer = bin_search(mid, A);
if(answer.first == true){
right = mid;
res = answer.second;
}
else left = mid + 1;
}
cout<<right<<endl;
for(int i = 0; i < N; i++){
for(auto &a : res[i])cout<<a<<" ";
cout<<0<<endl;
}
return 0;
}
