#include<bits/stdc++.h>
using namespace std;
#define fastio() ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vll vector<ll>
#define vpii vector<pii>
#define vpll vector<pll>
#define vvi vector<vi>
#define ff first
#define ss second
#define endl "\n"
#define pb(x) push_back(x)
#define pp() pop_back()
#define inf MAX_INT
#define dvg(x) cout<<#x<<" "<<x<<endl;
#define dvg2(x, y) cout<<#x<<" "<<x<<" "<<#y<<" "<<y<<endl;
#define dvgv(x) cout<<#x<<" { "; for(auto i : x) {cout<<i<<" ";} cout<<"}"<<endl;
#define dvgp(x) cout<<#x" {"<<x.ff<<", "<<x.ss<<"}"<<endl;
int dx[] {-1, 0, 1, 0, 1, 1, -1, -1};
int dy[] = {0, 1, 0, -1, 1, -1, 1, -1};
int const N = 1e5 + 10;
vpii v;
vvi ans;
int n, k, m;
bool ok(int x)
{
int day = 1, no_job = 1;
ans = vvi(n+1, vi());
for(int i = 0; i < m; i++){
while(day < v[i].ff) {
day++;
no_job = 1;
}
if(day > n) return 0;
if(day - v[i].ff >= x) return 0;
ans[day].pb(v[i].ss);
no_job++;
if(no_job > k) {
day++;
no_job = 1;
}
}
return 1;
}
int main()
{
fastio();
cin>>n>>k>>m;
v = vpii(m);
for(int i = 0; i < m; i++){
cin>>v[i].ff;
v[i].ss = i + 1;
}
sort(v.begin(), v.end());
int lo = 0, hi = 1e5 + 12;
while(lo < hi){
int mid = (hi + lo)/2;
if(ok(mid))
hi = mid;
else
lo = mid + 1;
}
cout<<lo<<endl;
ok(lo);
for(int i = 1; i <= n; i++) {
for(auto j : ans[i]) cout<<j<<" ";
cout<<0<<endl;
}
}
