#include<bits/stdc++.h>
using namespace std;
vector<pair<int, int>> arr;
int n, m , d;
vector<vector<int>> day;
bool f(int mm){
int del = 0;
day.clear();
day.resize(n+1);
queue<int> mac;
for(int i=0;i<mm;i++) mac.push(1);
for(int i=0;i<m;i++){
int r = mac.front();
del = max(r - arr[i].first, del);
if(del > d) return false;
day[r].push_back(arr[i].second);
mac.pop();
mac.push(r+1);
}
return true;
}
int main(){
cin>>n>>d>>m;
arr.resize(m);
for(int i=0;i<m;i++){
arr[i].second = i;
cin>>arr[i].first;
}
sort(arr.begin(), arr.end());
int mm;
int r = m;
int l = 1;
int ans = -1;
while(r >= l){
mm = l + (r - l)/2;
if(f(mm)){
r = mm - 1;
ans = mm;
}
else{
l = mm + 1;
}
}
f(ans);
cout<<ans<<endl;
for(int i=1;i<n+1;i++){
for(auto t : day[i]) cout<<t+1<<" ";
cout<<"0 \n";
}
}
