#include<bits/stdc++.h>
#pragma GCC optimize("-Ofast")
//#pragma GCC optimize("trapv")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#define I inline void
#define S struct
#define vi vector<int>
#define vii vector<pair<int,int>>
#define pii pair<int,int>
#define pll pair<ll,ll>
using namespace std ;
using ll = long long ;
using ld = long double ;
const int N = 1e6 + 7 , mod = 1e9 + 7 ;
const ll inf = 2e18 ;
// How interesting!
int n,d , m;
vector<pair<int,int> > v ;
bool check(int x){
int k = 0 ;
for(int i = 1 ;i <= n ; ++ i){
for(int j = 0 ;j < x && k < m; ++ j){
if(i > v[k].first + d)
return 0 ;
if(i>=v[k].first){
k ++ ;
}else break ;
}
}
return 1;
}
void answer(int x){
int k = 0 ;
for(int i = 0 ;i < n ; ++ i){
for(int j = 0 ;j < x && k < m ; ++ j){
cout<< v[k++].second + 1 <<" " ;
}
cout<<"0\n" ;
}
}
int main(){
ios_base::sync_with_stdio(0) ;
cin.tie(0) ;
//freopen("in.in" , "r" , stdin) ;
cin >> n >> d >> m ;
for(int i = 0 ;i < m ; ++ i){
int x ;
cin >> x ;
v.push_back({x , i}) ;
}
sort(v.begin() , v.end()) ;
int l = 1 , r = m ;
int ans = m ;
while(l<=r){
int mid = (l+r) >> 1;
if(check(mid)){
ans = mid ;
r = mid - 1;
}
else l = mid + 1;
}
cout<<ans <<"\n" ;
answer(ans) ;
return 0 ;
}
/*
- bounds sir (segtree = 4N, eulerTour = 2N, ...)
- a variable defined twice?
- will overflow?
- is it a good complexity?
- don't mess up indices (0-indexed vs 1-indexed)
- reset everything between testcases.
*/
