#include <bits/stdc++.h>
#define MAX_M 1000000
using namespace std;
int n, d, m;
pair<int, int> requests[MAX_M];
bool check(int x) {
int day = 2;
int index = x;
while(index < m) {
if(requests[index].first + d < day) {
return false;
}
day++;
index += x;
}
return true;
}
int main() {
cin >> n >> d >> m;
for(int i = 0; i < m; i++) {
cin >> requests[i].first;
requests[i].second = i + 1;
}
sort(requests, requests + m);
int l = 0, r = m;
int ans = 1;
while(l <= r) {
int mid = l + (r - l) / 2;
if(check(mid)) {
ans = mid;
r = mid - 1;
} else {
l = mid + 1;
}
}
cout << ans << "\n";
int ptr = 0;
for(int i = 0; i < n; i++) {
int counter = 0;
while(ptr < m && counter < ans) {
cout << requests[ptr].second << " ";
ptr++;
counter++;
}
cout << "0\n";
}
return 0;
}
