#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int mxN = 1e6;
pair<int, int> a[mxN];
int d, l, n;
vector<vector<int>> ans;
bool ok(int x){
ans.clear();
ans.resize(d);
int nx = x, cur = 1;
for(int i = 0;i<n;i++){
if(i == nx){
nx += x;
++cur;
}
if(a[i].f + l < cur){
return false;
}
ans[cur - 1].push_back(a[i].s);
}
return true;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> d >> l >> n;
ans.resize(d);
for(int i = 0;i<n;i++){
cin >> a[i].f;
a[i].s = i + 1;
}
sort(a, a + n);
int l = 1, r = n, x = n;
while(l <= r){
int mid = (l + r) / 2;
if(ok(mid)){
x = mid;
r = mid - 1;
}else{
l = mid + 1;
}
}
cout << x << '\n';
for(int i = 0;i<d;i++){
for(auto e : ans[i]){
cout << e << ' ';
}
cout << "0\n";
}
return 0;
}
