#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
const int M = 1e6 + 10;
pair<int,int> a[M];
int n,d,m;
bool check(int mid){
int ans = 0;
int k = 1;
for(int i = 0;i<m;i+=mid){
if(a[i].first > k){
k++;
i -= mid;
continue;
}
ans = max(ans,k - a[i].first);
k++;
}
// cout << mid << " " << k << " " << ans << "\n";
if(ans > d )//|| k > n - d)
return false;
else
return true;
}
signed main(){
iostream::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> d >> m;
for(int i =0;i<m;i++){
cin >> a[i].first;
a[i].second = i;
}
sort(a,a + m);
// for(int i = 0;i<m;i++)
// cout << a[i].first << " ";
// cout << "\n";
int l = (m + n - 1)/n ,r = m;
while(l < r){
int mid = (l + r - 1)/2;
if(check(mid))
r = mid;
else
l = mid + 1;
}
cout << l << "\n";
int idx = -1;
for(int i = 0;i<n;i++){
if(idx == m - 1)
cout << 0 << "\n";
else{
int j;
int temp = idx;
for(j = temp + 1;j<min(temp + l + 1, m);j++){
idx = j;
cout << a[idx].second + 1 << " ";
}
cout << 0 << "\n";
}
}
assert(idx == m - 1);
}
