#include <bits/stdc++.h>
using namespace std;
int n, d, m, x;
vector<pair<int, int>> vec;
bool solvable(int mcnt, bool printmode) {
vector<vector<int>> ans;
ans.push_back({});
for(int i=0;i<m;i++) {
while(ans.size() < vec[i].first) ans.push_back({});
if(ans.back().size() >= mcnt) ans.push_back({});
if(ans.size() - vec[i].first > d) return 0;
ans.back().push_back(vec[i].second);
}
while(ans.size() < n) ans.push_back({});
if(printmode) {
for(auto &e:ans) {
for(auto &E:e) cout << E << ' ';
cout << "0\n";
}
}
return 1;
}
int main() {
cin.tie(0) -> sync_with_stdio(0);
cin >> n >> d >> m;
for(int i=1;i<=m;i++) {
cin >> x;
vec.emplace_back(x, i);
}
sort(vec.begin(), vec.end());
int l = 1, r = m, mid = -1;
while(l <= r) {
mid = (l+r) >> 1;
if(solvable(mid, 0)) r = mid - 1;
else l = mid + 1;
}
cout << l << '\n';
auto e = solvable(l, 1);
}
