#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pi3 = pair<int,pii>;
#define ON(n , k) ( (n) | ( 1 << (k) ))
#define OFF(n ,k) ( (n) & ( ~( 1 << (k))))
#define ISON(n ,k) ( ( (n)>>(k) ) & (1) )
#define F first
#define S second
const int N = 2e5+5;
const int mod = 1e9+7;
const int INF = 1e9+9;
const double PI = 3.1415926536;
int dx[10] = {0, 0, 1, -1, 1, 1, -1, -1, 0};
int dy[10] = {1, -1, 0, 0, 1, -1, 1, -1, 0};
char str[N];
int n, d, m;
vector<pii>v;
vector<vector<int>> v1(N), ans(N);
bool ok(int mid)
{
for(int i = 0; i < n; i++)
{
v1[i].clear();
}
int i = 0;
for(int j = 1; j <= n; j++)
{
for(int x = 0; x < mid; x++)
{
if(v[i].F > j)break;
if(v[i].F + d < j)return false;
v1[j - 1].push_back(v[i].S);
i++;
if(i == m)return true;
}
}
return false;
}
void solve()
{
scanf("%d%d%d", &n, &d, &m);
for(int i = 1; i <= m; i++)
{
int x;
scanf("%d", &x);
v.push_back({x, i});
}
sort(v.begin(), v.end());
int l = 0, r = m+2, mid;
while(l + 1 < r)
{
mid = l + (r - l)/2;
if(ok(mid))
{
r = mid;
ans = v1;
}
else
{
l = mid;
}
}
printf("%d\n", r);
for(int j = 0; j < n ; j++)
{
for(int x : ans[j])
{
printf("%d ", x);
}
printf("0\n");
}
}
int main()
{
//freopen("", "r", stdin);
//freopen("", "w", stdout);
/*
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
*/
int T;
T = 1 ;
//scanf("%d" , &T);
while(T--)
{
// init();
solve();
}
return 0;
}
