#include <bits/stdc++.h>
using namespace std;
#define int long long
mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
void Solve() {
int n, d, m;
cin >> n >> d >> m;
vector<pair<int, int> > a(m + 1);
for(int i = 1; i <= m; i++) {
cin >> a[i].first;
a[i].second = i;
}
sort(a.begin() + 1, a.end());
a[0] = {-1, -1};
int l = 1, r = m;
int mid, ans = r + 1;
while(l <= r) {
mid = (l + r) >> 1;
int cur_day = a[1].first, cur_cnt = 0, f = 0;
for(int i = 1; i <= m; i++) {
if(cur_cnt == mid) {
cur_day++;
cur_cnt = 0;
}
if(a[i].first > cur_day) {
cur_day = a[i].first;
cur_cnt = 0;
}
if(cur_day - a[i].first > d) {
f = 1;
break;
}
cur_cnt++;
}
if(f == 1) {
l = mid + 1;
}
else {
r = mid - 1;
ans = mid;
}
}
cout << ans << "\n";
int pos = 1;
for(int i = 0; i < n; i++) {
int cur_cnt = 0;
while(pos != m + 1 && a[pos].first <= i + 1 && cur_cnt != ans) {
cur_cnt++;
cout << a[pos++].second << " ";
}
cout << "0\n";
}
}
int32_t main() {
auto begin = std::chrono::high_resolution_clock::now();
ios_base::sync_with_stdio(0);
cin.tie(0);
int t = 1;
//cin >> t;
while(t--) {
Solve();
}
auto end = std::chrono::high_resolution_clock::now();
auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n";
return 0;
}
