#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
int n, d, m;
pair < int, int > a[N];
inline bool check(int x){
int i = 1, day = 0;
while(i <= m){
day += 1;
int j = i;
while(j <= min(m, i + x - 1) && day >= a[j].first){
if(a[j].first + d < day){
return false;
}
j += 1;
}
i = j;
}
return true;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> d >> m;
for(int i = 1; i <= m; i++){
cin >> a[i].first;
a[i].second = i;
}
sort(a + 1, a + m + 1);
int l = 1, r = m;
while(l < r){
int mid = (r + l) >> 1;
if(check(mid)){
r = mid;
}
else{
l = mid + 1;
}
}
cout << l << "\n";
int i = 1, day = 0;
for(int it = 1; it <= n; it++){
day += 1;
int j = i;
while(j <= min(m, i + l - 1) && day >= a[j].first){
cout << a[j].second << " ";
j += 1;
}
cout << "0\n";
i = j;
}
}
