#include<bits/stdc++.h>
#define pb push_back
using namespace std;
typedef long long ll;
const int Maxn = 1e5 + 10;
vector<int> rec[Maxn], op[Maxn];
int cnt[Maxn];
int n, m, d;
bool check(int c){
for(int i = 1; i <= n; i++) cnt[i] = rec[i].size();
int p = 1, done = 0, free, rem;
for(int i = 1; i <= n; i++){
p = max(p, i - d);
free = c;
while((p <= i) && (free)){
rem = min(free, cnt[p]);
free -= rem;
cnt[p] -= rem;
done += rem;
if(cnt[p] == 0) p++;
}
}
return (done == m);
}
void solve(int c){
int p = 1, free;
for(int i = 1; i <= n; i++){
p = max(p, i - d);
free = c;
while((p <= i) && (free)){
if(rec[p].size() == 0){
p ++;
continue;
}
free --;
op[i].pb(rec[p].back());
rec[p].pop_back();
}
}
return ;
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> d >> m;
int v;
for(int i = 1; i <= m; i++){
cin >> v;
rec[v].pb(i);
}
int l = 0, r = m, mid;
while(l + 1 < r){
mid = (l + r) >> 1;
if(check(mid)) r = mid;
else l = mid;
}
cout << r << '\n';
solve(r);
for(int i = 1; i <= n; i++){
for(auto x : op[i]) cout << x << " ";
cout << "0\n";
}
return 0;
}
/*
8 2 12
1 2 4 2 1 3 5 6 2 3 6 4
*/
