#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define endl '\n'
#define mask(i) (1LL << (i))
#define y1 BinhKhung
using namespace std;
const int mxN = 2e5 + 7;
const int inf = 1e9 + 7;
const ll mod = 1e9 + 7;
const ll infll = 1e18 + 7;
const int offset = 1e5;
int numday , maxday , numjob;
pair<int , int> job[mxN];
vector<int> ans[mxN];
bool ok(int x)
{
int day = 1;
for(int i = 1 ; i <= numday ; i++) {
for(int j = 1 ; j <= x ; j++) {
if(job[day].fi <= i && i <= job[day].fi + maxday) {
day++;
if(day > numjob) return true;
}
else break;
}
}
return day > numjob;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
//freopen("task.inp" , "r" , stdin);
//freopen("task.out" , "w" , stdout);
cin >> numday >> maxday >> numjob;
for(int i = 1 ; i <= numjob ; i++) cin >> job[i].fi;
for(int i = 1 ; i <= numjob ; i++) job[i].se = i;
sort(job + 1 , job + 1 + numjob);
int lo = 1 , hi = numjob;
while(lo + 1 < hi) {
int m = (lo + hi) / 2;
if(ok(m)) hi = m;
else lo = m;
}
int res = 0;
if(ok(lo)) res = lo;
else res = hi;
cout << res << endl;
int day = 1;
for(int i = 1 ; i <= numday ; i++) {
for(int j = 1 ; j <= res ; j++) {
if(job[day].fi <= i && i <= job[day].fi + maxday) {
ans[i].push_back(job[day].se);
day++;
if(day > numjob) break;
}
else break;
}
if(day > numjob) break;
}
for(int i = 1 ; i <= numday ; i++) {
for(int j : ans[i]) cout << j << ' ';
cout << 0 << endl;
}
return 0;
}
