#undef _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
#define fi first
#define si second
typedef pair<int,int> pi;
typedef tuple<int,int,int> ti;
void debug_out() {cerr<<endl;}
template <typename Head, typename... Tail>
void debug_out(Head _H, Tail... _T) {cerr<<" "<<to_string(_H);debug_out(_T...);}
#define debug(...) cerr<<"["<<#__VA_ARGS__<<"]:",debug_out(__VA_ARGS__)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 100010;
int n, d, m;
pi arr[MAXN];
vector<int> ans[MAXN];
bool good(int num) {
vector<int> cur[n + 1];
int j = 1;
for (int i = 1; i <= n; ++i) {
int cnt = num;
while (j <= m && cnt && arr[j].fi <= i) {
if (i - arr[j].fi > d) return false;
cur[i].pb(arr[j].si);
++j;
--cnt;
}
}
if (j >= m) {
for (int i = 1; i <= n; ++i) ans[i] = cur[i];
return true;
}
return false;
}
int main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> d >> m;
for (int i = 1; i <= m; ++i) cin >> arr[i].fi, arr[i].si = i;
sort(arr + 1, arr + 1 + m);
int lo = 0, hi = 1e9;
while (lo + 1 < hi) {
int mid = (lo + hi) >> 1;
if (good(mid)) hi = mid;
else lo = mid;
}
cout << hi << '\n';
for (int i = 1; i <= n; ++i) {
for (auto j: ans[i]) cout << j << ' ';
cout << 0 << '\n';
}
return 0;
}
