//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("avx,avx2")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,avx,avx2")
//#pragma GCC optimize("trapv")
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define mpr make_pair
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
const int nmax = 100011, mod = 1000000007, inf = 2000010000, key = 200003, lg = 20, block = 300;
const ll infll = 4000000000000000000;
const ld eps = 1e-9;
bool check(vector<int> vc, int d, int ans) {
int cur = 1;
int n = vc.size();
for(int i = 1; i < n; i++) {
int cnt = ans;
while(cnt > 0 && cur <= i) {
int t = min(cnt, vc[cur]);
cnt -= t;
vc[cur] -= t;
if(vc[cur] == 0)
cur++;
}
if(i - d >= cur)
return 0;
}
return 1;
}
void solve()
{
int n, m, d;
cin >> n >> d >> m;
vector<pair<int, int>> vc(m);
vector<int> cnt(n + 1, 0);
for(int i = 0; i < m; i++) {
int a;
cin >> a;
vc[i] = mpr(a, i + 1);
cnt[a]++;
}
sort(all(vc));
int l = 0, r = m;
while(l + 1 < r) {
int md = (l + r) / 2;
if(check(cnt, d, md))
r = md;
else
l = md;
}
int ans = r;
cout << ans << "\n";
int cur = 0;
for(int i = 0; i < n; i++) {
for(int j = 0; j < ans; j++) {
if(cur == m)
break;
cout << vc[cur].second << " ";
cur++;
}
cout << "0\n";
}
return ;
}
int main()
{
//freopen("cruise.in","r",stdin);
//freopen("cruise.out","w",stdout);
ios_base::sync_with_stdio(0);cin.tie(0);
srand(8713);
//init();
int t = 1;
//cin >> t;
//int t_ = t;
//t = rdi();
while(t--) {
//cout << "Case #" << t_ - t << ": ";
solve();
}
//flush();
return 0;
}
/*
6 6 0
1 2
0 1
0 3
3 4
4 5
1 5
1
3
5 5 2
1 0
1 2
3 2
1 3
4 2
2
3 1
*/
