#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
constexpr ll MAXN=2e5+5,MAXV=3e5,MOD=1e9+7,INF=1e18;
ll n,m,i,j,p,k,ans,a[MAXN],dem,st,en;
vector<ll> day[MAXN];
bool check(ll m){
ll cnt=0;
for(ll i=n+k;i>=1;i--){
cnt=max(0ll,cnt+(a[i]-m));
}
if(cnt>0) return false;
return true;
}
struct h{
ll a,id;
} b[MAXN];
bool cmp(h x,h y){
return x.a<y.a;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin>>n>>k>>m;
ll l=1,r=n,best=0;
for(i=1;i<=m;i++)
cin>>p,a[k+p]++,b[i].a=k+p,b[i].id=i;
while(l<r){
ll m=(l+r)/2;
if(check(m)){
best=m;
r=m;
}
else l=m+1;
}
if(check(l)) best=l;
sort(b+1,b+m+1,cmp);
ll cur=m;
for(i=n+k;i>=1;i--){
ll cnt=0;
while(cur>0&&cnt<best&&b[cur].a>=i){
day[i].pb(b[cur].id);
cur--;
cnt++;
}
}
cout<<best<<'\n';
for(i=1;i<=n;i++){
for(ll x:day[i])
cout<<x<<" ";
cout<<0<<'\n';
}
}
