#include <bits/stdc++.h>
using namespace std;
#define pi pair<int, int>
#define f first
#define s second
int n, d, m;
int j[100001];
pi jd[1000000];
bool q(int x) {
int cd = 0;
int cj[100001];
for (int i = 1; i <= n; ++i) {
cj[i] = j[i];
}
for (int i = 1; i <= n; ++i) {
if (cj[i] % x == 0 || cj[i] < x) {
if (cd + cj[i] / x >= d) return false;
cd += cj[i] / x;
}
else {
if (cd + cj[i] / x + 1 >= d) return false;
cd += cj[i] / x + 1;
}
if (i != n) {
if (cj[i + 1] >= x - (cj[i] - x * (cj[i] / x)))
cj[i + 1] -= x - (cj[i] - x * (cj[i] / x));
else cj[i + 1] = 0;
}
}
return true;
}
int main() {
cin >> n >> d >> m;
for (int i = 0; i < m; ++i) {
int a; cin >> a;
++j[a];
jd[i] = {a, i + 1};
}
sort(jd, jd + m);
int l = 0, r = 1000000;
for (r ++; l < r; ) {
int m = l + (r - l) / 2;
if (q(m)) r = m;
else l = m + 1;
}
cout << l << endl;
for (int i = 0; i < m; i += l) {
for (int j = 0; j < l; ++j) {
cout << jd[i + j].s << ' ';
}
cout << 0 << endl;
}
for (int i = 0; i < d; ++i) cout << 0 << endl;
}
