#include <iostream>
#include <vector>
bool run(std::vector<int> a, int d, int x, std::vector<std::vector<int>>& answer, std::vector<std::vector<int>> ids) {
int i = a.size() - d - 1;
for (int j = a.size() - 1; i >= 0 && j >= 0; --j) {
//std::cout << i << ' ' << j << '\n';
int v = std::min(a[i], x);
a[i] -= v;
while (v > 0) {
//std::cout << "To " << j << " add " << ids[i].back() << '\n';
answer[j].push_back(ids[i].back());
ids[i].pop_back();
--v;
}
if (i == j && a[i] != 0) return false;
if (a[i] == 0) --i;
if (a[i] < 0) break;
}
return true;
}
int main() {
int n, d, m;
std::cin >> n >> d >> m;
std::vector<int> a(n + 1, 0);
std::vector<std::vector<int>> ids(n + 1, std::vector<int>());
for (int i = 0; i < m; ++i) {
int tmp; std::cin >> tmp;
a[tmp]++;
ids[tmp].push_back(i + 1);
}
int l = 0;
int r = n;
std::vector<std::vector<int>> answer;
// (l, r]
while (l + 1 < r) {
answer = std::vector<std::vector<int>>(n + 1, std::vector<int>());
int m = (l + r) / 2;
if (run(a, d, m, answer, ids)) {
r = m;
} else {
l = m;
}
}
answer = std::vector<std::vector<int>>(n + 1, std::vector<int>());
run(a, d, r, answer, ids);
std::cout << r << '\n';
for (int i = 1; i <= n; ++i) {
for (size_t j = 0; j < answer[i].size(); ++j) {
std::cout << answer[i][j] << ' ';
}
std::cout << "0\n";
}
}
