#include <bits/stdc++.h>
using namespace std;
const int M = 100005;
#define F first
#define S second
int n, d, m;
pair <int,int> a[M];
bool check(int mid)
{
int pos = 1;
for(int i = 1; i <= n; ++i)
for(int j = 1; j <= mid && pos <= m; ++j, ++pos) if(i - a[pos].F > d) return 0;
return (pos == m + 1);
}
int main()
{
cin >> n >> d >> m;
for(int i = 1; i <= m; ++i) cin >> a[i].F, a[i].S = i;
sort(a + 1, a + 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 << endl;
int pos = 1;
for(int i = 1; i <= n; ++i){
for(int j = 1; j <= r && pos <= m; ++j, ++pos) cout << a[pos].S << " ";
cout << 0 << endl;
}
}
