#include <bits/stdc++.h>
using namespace std;
const int M = 1000005;
#define ff first
#define ss second
int n, d, m;
pair <int,int> tasks[M];
bool check(int mid){
int pos = 1;
for(int i = 1; i <= n; ++i)
for(int j = 1; j <= mid && pos <= m && tasks[pos].ff <= i; ++j) if(i - tasks[pos++].ff > d) return false;
return (pos == m + 1);
}
int main(){
cin >> n >> d >> m;
for(int i = 1; i <= m; ++i) cin >> tasks[i].ff, tasks[i].ss = i;
sort(tasks + 1, tasks + m + 1);
int l = 1, r = m + 1;
while(l < r){
int mid = (l + r) / 2;
if(check(mid)) r = mid;
else l = mid + 1;
}
cout << r << '\n';
int pos = 1;
for(int i = 1; i <= n; ++i){
for(int j = 1; j <= r && pos <= m && tasks[pos].ff <= i; ++j, ++pos) cout << tasks[pos].ss << ' ';
cout << 0 << '\n';
}
}
