#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <string>
#include <map>
#include <string>
#include <set>
#include <queue>
#include <cmath>
#include <tuple>
#include <stack>
#include <numeric>
#include <climits>
#include <deque>
#include <chrono>
#include <unordered_map>
#include <cstring>
using namespace std;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#define systemwait system("read -p \"Press Enter to continue...\"");
#else
#define debug(x...)
#define systemwait
#endif
#define int long long
#define endl '\n'
#define all(x) (x).begin(),(x).end()
#define sqsq(x) (x)*(x)
#define pii pair<int,int>
#define vi vector<int>
#define vii vector<pii>
const int INF=1e9+7;
const int MOD=1e9+7;
//const int MOD=998244353;
const int maxn=1e6+10;
pii pool[maxn];
int N,D,M,ans;
bool Check(int x) {
int pos=0;
for(int i=1;i<=N;i++) {
for(int j=1;j<=x;j++) {
if(pos<M) {
pos++;
}
if(i-pool[pos].first>D) {
return false;
}
if(pos==M) {
return true;
}
}
}
return false;
}
int BinSearch() {
int l=1,r=1e9;
while(l<=r) {
int mid=(l+r)/2;
if(Check(mid)) {
r=mid-1;
} else {
l=mid+1;
}
}
return l;
}
void solve() {
//--------Initiallize Boundless--------
//--------Input--------
cin>>N>>D>>M;
for(int i=1;i<=M;i++) {
cin>>pool[i].first;
pool[i].second=i;
}
//--------Initiallize Bounded--------
//--------No fluff real stuff--------
sort(pool+1,pool+M+1);
ans=BinSearch();
cout<<ans<<endl;
int pos=0;
for(int i=1;i<=N;i++) {
for(int j=1;j<=ans;j++) {
if(pos<M) {
pos++;
cout<<pool[pos].second<<" ";
}
}
cout<<0<<endl;
}
return;
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(0);
int TT=1;
//cin>>TT;
for(int i=1;i<=TT;++i) {
solve();
}
return 0;
}
