#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e5 + 100;
vector <int> work[N], on[N];
int n, d, m;
bool bin(int lim) {
for (int i = 1; i <= n; i++)
work[i].clear();
int j = 1, pos = 0, cnt = 0;
for (int i = 1; i <= n; i++) {
int cc = 0;
while (j <= i && cc < lim) {
if (pos == sz(on[j])) {
j++;
pos = 0;
} else {
if (i - j > d)
return 0;
work[i].pb(on[j][pos]);
pos++;
cnt++;
cc++;
}
}
}
if (cnt < m)
return 0;
return 1;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> d >> m;
for (int i = 1; i <= m; i++) {
int x;
cin >> x;
on[x].pb(i);
}
int l = 1, r = m, ans = 0;
while (l <= r) {
int mid = (l + r) / 2;
if (bin(mid)) {
ans = mid;
r = mid - 1;
} else {
l = mid + 1;
}
}
bin(ans);
cout << ans << '\n';
for (int i = 1; i <= n; i++) {
for (auto x : work[i])
cout << x << " ";
cout << 0 << '\n';
}
return 0;
}
