#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define FOR(I, L, R) for(int I(L) ; I <= (int)R ; ++I)
#define FOD(I, R, L) for(int I(R) ; I >= (int)L ; --I)
#define FOA(I, A) for(auto &I : A)
#define print(A,L,R) FOR(OK, L, R){if(A[OK]<=-oo / 10||A[OK]>=oo)cout<<"- ";else cout<<A[OK]<<' ';}cout<<'\n';
#define prints(A) FOA(OK, A){cout<<OK<<' ';}cout << '\n';
#define printz(A,L,R) FOR(OK, 0, L){FOR(KO, 0, R){if(A[OK][KO]>-oo&&A[OK][KO]<oo)cout<<A[OK][KO]<<' ';else cout << "- ";} cout << '\n';}cout << '\n';
#define fs first
#define sd second
#define ii pair<int,int>
#define iii pair<int, ii>
#define all(A) A.begin(), A.end()
#define quickly cin.tie(0) -> ios_base::sync_with_stdio(0);
const int N = 1e6 + 5;
const int mod = 1e9 + 7;
const int oo = 1e9;
int n, m, d;
vector<int> sweep[N];
priority_queue<ii, vector<ii>, greater<ii>> pq;
vector<int> ans[N];
bool calc(int x){
while(!pq.empty()){
pq.pop();
}
FOR(i, 1, n){
ans[i].clear();
FOA(v, sweep[i]){
pq.push({i, v});
}
FOR(re, 1, x){
if(pq.empty()){
break;
}
ans[i].push_back(pq.top().sd);
pq.pop();
}
if(!pq.empty() && pq.top().fs + d == i){
return 0;
}
}
return 1;
}
signed main(){ quickly
cin >> n >> d >> m;
FOR(i, 1, m){
int x;
cin >> x;
sweep[x].push_back(i);
}
int l = 1, r = m;
int res = 0;
while(l <= r){
int mid = (l + r) >> 1;
if(calc(mid)){
r = mid - 1;
res = mid;
}
else{
l = mid + 1;
}
}
calc(res);
cout << res << '\n';
FOR(i, 1, n){
FOA(j, ans[i]){
cout << j <<' ';
}
cout << "0\n";
}
}
