#include <bits/stdc++.h>
#define f0(i, n) for(int i(0); i < (n); i++)
#define f1(i, n) for(int i(1); i <= n; i++)
using namespace std;
typedef long long ll;
const int N = 100002;
int n, d, m;
pair <int, pair <int, int> > a[N*10];
vector <vector <int> > v, b;
bool check(int x){
f1(i, n) v[i].clear();
int ma = a[1].first, cur = 0;
f1(i, m){
while(ma < a[i].first) ma++;
cur++;
if(cur <= x){
v[ma].emplace_back(a[i].second.second);
}
else{
cur = 1;
ma++;
if(ma > n) return 0;
v[ma].emplace_back(a[i].second.second);
}
}
return 1;
}
int main(){
ios_base::sync_with_stdio(0);
cin >> n >> d >> m;
v.resize(n + 1);
b.resize(n + 1);
f1(i, m){
int x; cin >> x;
a[i] = {x, {x + d, i}};
}
sort(a + 1, a + m + 1);
int l = 1, r = n, ans = n;
while(l <= r){
int mid = (l + r)/2;
if(check(mid)){
r = mid - 1, ans = mid;
f1(i, n){
b[i].clear();
for(auto x:v[i]){
b[i].emplace_back(x);
}
}
}
else l = mid + 1;
}
cout << ans << endl;
f1(i, n){
for(auto x:b[i]) cout << x << " ";
cout << 0 << endl;
}
}
