#include <iostream>
#include <algorithm>
#include <vector>
#include <set>
#include <queue>
#include <map>
#include <cmath>
#include <iomanip>
#define ll long long
using namespace std;
int N, D, M;
pair<int, int> arr[1000000];
bool check (int val) {
//cout << "val: " << val << endl;
int index = 0;
for (int day = 1; day <= N; day++) {
index += val;
//cout << "day: " << day << " index: " << index << endl;
if (index - 1 < M && arr[index - 1].first + D < day) {
return false;
} else if (index >= M) {
return true;
}
}
if (index >= M) {
return true;
} else {
return false;
}
}
void printAns (int val) {
int index = 1;
for (int day = 1; day <= N; day++) {
for (int i = index; i < index + val && i <= M; i++) {
cout << arr[i].second << " ";
}
index += val;
cout << "0" << endl;
}
}
int main() {
cin >> N >> D >> M;
for (int i = 1; i <= M; i++) {
cin >> arr[i].first;
arr[i].second = i;
}
sort(arr+1, arr + M+1, [](pair<int, int> a, pair<int, int> b) {
return a.first < b.first;
});
// cout << "arr: " << endl;
// for (int i = 1; i <= M; i++) {
// cout << arr[i].first << " " << arr[i].second << endl;
// }
int low = 1;
int high = 1e7;
while (low < high) {
int mid = (low + high) / 2;
if (check(mid)) {
high = mid;
} else {
low = mid + 1;
}
}
cout << low << endl;
printAns(low);
}
