#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
vector<pair<int, int>> s(1<<20);
int n, m, d;
bool verdict(int mid, bool print = 0){
int lst = 0, R = 0;
for (int i=1;i<=n;i++){
while (s[R+1].first == i)
R++;
if (print == 1){
for (int j=lst+1;j <= min(lst + mid, R);j++)
cout<<s[j].second<<' ';
cout<<"0\n";
}
lst = min(lst + mid, R);
if (lst < m and s[lst+1].first + d <= i)
return 0;
}
return 1;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
cin>>n>>d>>m;
for (int i=1, j;i<=m;i++){
cin>>j;
s[i] = {j, i};
}
sort(begin(s) + 1, begin(s) + m + 1);
int l = 0, r = m;
while (l + 1 < r){
int mid = (l + r) / 2;
if (verdict(mid))
r = mid;
else
l = mid;
}
cout<<r<<endl;
verdict(r, 1);
}
