#include <bits/stdc++.h>
#define fr first
#define se second
#define rep(i,a,b) for(int i = a; i < (b); ++i)
#define repr(i,a,b) for(int i = a; i > (b); --i)
#define sz(x) (int)(x).size()
#define all(x) (x).begin(),(x).end()
#define IN(i,l,r) (l<i&&i<r)
#define pb push_back
using namespace std;
typedef pair<int,int> pi;
typedef vector<int> vi;
typedef long long ll;
const int U = 1e6+2;
int N,D,M;
pi job[U];
int jd[U/10 + 1];
bool check(int m){
int day = 0,t = 0;
while(day < N && t < M){
++day;
if(job[t].fr + D < day){
return false;
}
t = min(t+m,jd[day]);
if(job[t-1].fr + D < day){
return false;
}
}
return true;
}
int main(){
cin.tie(0)->sync_with_stdio(false);
cin >> N >> D >> M;
rep(i,0,M){
cin >> job[i].fr;
jd[job[i].fr] += 1;
job[i].se = i+1;
}
rep(i,2,N+1) jd[i] += jd[i-1];
sort(job,job+M);
int lo=1,hi=U;
while(lo < hi){
ll m = (lo+hi)/2;
if(check(m)){
hi = m;
}else{
lo = m+1;
}
}
cout << hi << '\n';
int day = 0,t = 0;
while(day < N){
++day;
int t_ = min(t+hi,jd[day]);
rep(i,t,t_){
cout << job[i].se << ' ';
}
cout << "0\n";
t = t_;
}
}
