#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
#define FOR(i,a,b) for(int i = (a) , _b = (b); i <= _b; ++i)
#define MASK(x) ((LL)(1)<<(x))
#define BIT(mask , x) (((mask)>>(x))&(1))
template<class X , class Y>
bool maximize(X &x , Y y){
if (x<y) return x=y,true; else return false;
}
template<class X,class Y>
bool minimize(X &x, Y y){
if (x>y) return x=y,true; else return false;
}
template<class T>
void compress(vector<T>&data){
sort(data.begin() , data.end()) ;
data.resize(unique(data.begin() , data.end()) - data.begin());
return;
}
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
int Rand(int l,int r){
return uniform_int_distribution<int>(l,r)(rng);
}
const int N = (int) 1e6;
const int MAXLOG = (int)18;
vector<int>days[N+2];
int id[N+2] = {} , a[N+2] = {};
int n , m , d;
bool check(int length){
for(int i = 1 , cur = 1; i <= m; i += length , ++cur){
int x = min(m , i + length - 1);
if (a[id[i]] + d < cur) return false;
}
return true;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0) ; cout.tie(0);
#define name "main"
if (fopen(name".inp","r")){
freopen(name".inp","r",stdin);
freopen(name".out","w",stdout);
}
cin >> n >> d >> m;
FOR(i,1,m) cin >> a[i] , id[i] = i;
sort(id+1,id+m+1,[&](int i,int j){
return a[i] < a[j];
});
int low = 1 , high = m , ans = -1;
while (low<=high){
int mid = (low+high) / 2;
if (check(mid)){
ans = mid , high = mid-1;
}
else low = mid + 1;
}
cout << ans << '\n';
int idx = 1;
for(int i = 1; i <= n; ++i){
for(int j = idx; j <= min(m , idx + ans - 1); ++j) cout << id[j] << ' '; cout << 0 << '\n';
idx += ans;
}
}
