#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
#define getar(ar,n) for(ll i=0;i<n;++i) cin>>ar[i]
#define show(n) cout<<n<<'\n'
#define all(v) v.begin(), v.end()
#define br cout<<"\n"
#define pb push_back
#define nl '\n'
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define ret return
#define ll long long
#define ld long double
#define sza(x) ((int)x.size())
const int mxN = 1e6 + 500;
const ll MOD = 1e9 + 7;
const ll INF = 1e9;
const ld EPS = 1e-9;
vector<pair<ll,ll>> ar;
ll n,m,d,x;
bool good(ll mid){
for(ll day=1,curr=0;day<=n&&curr<m;++day){
for(ll mach=1;curr<m&&mach<=mid&&ar[curr].first<=day;++mach){
if(ar[curr++].first+d<day) return 0;
}
}
return 1;
}
void solve(ll tc) {
cin>>n>>d>>m;
for(ll i=0;i<m;++i){
cin>>x;
ar.pb({x,i});
}
sort(all(ar));
ll start=1,end=1e5+10,ans=INF;
while(start<=end){
ll mid=start+(end-start)/2;
if(good(mid)){
ans=mid;
end=mid-1;
}else{
start=mid+1;
}
}
vector<vector<ll>> ans2(n+1);
ll curr=0;
for(ll day=1;day<=n&&curr<m;++day){
for(ll j=0;j<ans&&curr<m&&ar[curr].first<=day;++j){
ans2[day].pb(ar[curr++].second+1);
}
}
show(ans);
for(ll i=1;i<=n;++i){
for(auto itt:ans2[i]){
cout<<itt<<" ";
}
cout<<0<<'\n';
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
solve(69);
return 0;
}
