#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, d, m;
cin >> n >> d >> m;
vector<vector<int>> J(n);
for(int i=0; i<m; i++) {
int c; cin >> c;
J[c-1].push_back(i+1);
}
int lo=0, hi=m;
while(lo < hi) {
int mid = (lo + hi) / 2;
int t = 0;
int rem=mid;
bool works=true;
for(int i=0; i<n && works; i++) {
int count = J[i].size();
count -= rem;
t++;
rem=mid;
if(count<0) continue;
while(count>0) {
count-=mid;
if(count<0) rem=-count;
else t++;
}
if(t-i>d) works=false;
}
if(works) hi = mid;
else lo = mid+1;
}
cout << lo << "\n";
int count=0;
int acc=0;
for(int i=0; i<n; i++) {
for(int j : J[i]) {
if(count>=lo) {
cout << 0 << "\n" << j << " ";
acc++;
count=1;
}
else {
cout << j << " ";
count++;
}
}
if(acc<=i) {
cout << 0 << "\n";
count=0;
acc++;
}
}
}
