#include <iostream>
#include <algorithm>
#include <utility>
#include <vector>
#include <bit>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <string>
#include <time.h>
#include <random>
#include <iomanip>
#include <inttypes.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <class T>
using Tree = tree<T, null_type, std::less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("O3,Ofast")
#define si(n) scanf("%lld", &n);
#define sl(n) scanf("%lld", &n);
#define sc(n) scanf("%c", &n);
#define sf(n) scanf("%f", &n);
#define slf(n) scanf("%lf", &n);
#define fi first
#define se second
// #define int long long
#define pb push_back
#define mp make_pair
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define dbg(x) std::cerr << #x << ": " << x << std::endl;
typedef std::set<int> si;
typedef std::pair<int, int> pi;
typedef std::vector<int> vi;
typedef std::vector<std::vector<int>> dvi;
typedef std::unordered_map<int , int> mi;
const float EPS = 1e-9;
const float PI = acos(-1);
const int MAXN = 1000005;
const int MOD = 1000000007;
const int INF = INT64_MAX;
int gcd(int a, int b) {return (b == 0) ? a : gcd(b, a%b);}
int lcm(int a, int b) {return a/gcd(a, b) * b;}
int N, D, M;
std::pair<int, vi> freq[MAXN];
bool isPossibel(int exMachina) {
for(int i = 1; i <= N; ++i) {
if((freq[i].fi+exMachina-1)/exMachina > D) return false;
}
return true;
}
signed main()
{
std::ios::sync_with_stdio(0);
std::cin.tie(0);
std::cin>>N>>D>>M;
for(int i = 0; i < M; ++i) {
int num; std::cin>>num;
freq[num].fi++;
freq[num].se.pb(i+1);
}
int low = 1, high = 1e6, mid = 0, ans = 0;
while(low < high) {
mid = low + (high-low)/2;
if(isPossibel(mid)) {
high = mid;
} else {
ans = mid+1;
low = mid+1;
}
}
std::cout<<ans<<"\n";
for(int i = 1; i <= N; ++i) {
for(int j = 0; j < ans && j < (int)freq[i].se.size(); ++j) {
std::cout<<freq[i].se[j]<<" ";
} std::cout<<0<<"\n";
for(int j = freq[i].se.size()-1; j >= ans; --j) {
freq[i+1].se.pb(freq[i].se.back());
freq[i].se.pop_back();
}
}
return 0;
}
