#include <bits/stdc++.h>
using namespace std;
void quit() {
cout.flush();
exit(0);
}
long long n, d, m;
vector <pair<long long ,long long>> requests;
bool good(long long machines){
for(long long i = 0; i < m; i++){
if((i/machines+1)-requests[i].first>d){
return false;
}
}
return true;
}
int main(void){
//freopen("qwer.in", "r", stdin);
//freopen("qwer.out", "w", stdout);
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> d >> m;
requests.resize(m);
for(long long i = 0; i < m; i++){
cin >> requests[i].first;
requests[i].second = i+1;
}
sort(requests.begin(), requests.end());
long long s = 0, e = m;
while(s!=e){
long long mid = (s+e)/2;
if(good(mid)){
e=mid;
}
else{
s=mid+1;
}
}
cout << e << "\n";
long long num_left = n;
for(long long i = 0; i < m; i+=e){
for(long long j = i; j < min(m, i+e); j++){
cout << requests[j].second << " ";
}
num_left--;
cout << "0\n";
}
for(long long i = 0; i < num_left; i++){
cout << "0\n";
}
quit();
}
