#include<bits/stdc++.h>
// #pragma GCC target ("avx,avx2,fma")
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
typedef long long ll;
typedef long double ld;
#define SPEED ios_base::sync_with_stdio(false); cin.tie(0), cout.tie(0)
#define rall(v) (v).rbegin(),(v).rend()
#define all(v) (v).begin(),(v).end()
#define OK cerr<<"OK"<<endl<<flush
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define F first
#define S second
#define y0 jahdakdh
#define y1 jahsadakdakdh
#define endl '\n'
using namespace std;
const ll MOD=1e9+7;
//mt19937 rng(std::chrono::system_clock::now().time_since_epoch().count());
int n, d, m;
pii a[1000005];
bool check(int x)
{
int day=1;
while(day<=n)
{
if(day*x>m) break;
//cout<<x<<' ' <<day<<' '<<a[day*x-1].F<<endl;
if(a[day*x-1].F<day) return 0;
day++;
}
return 1;
}
int main()
{
SPEED;
cin>>n>>d>>m;
for(int i=0; i<m; i++)
{
cin>>a[i].F;
a[i].F+=d;
a[i].S=i+1;
}
sort(a, a+m);
int l=1, r=m, mid, pos=0;
while(l<=r)
{
mid=(l+r)>>1;
if(check(mid)) r=mid-1;
else l=mid+1;
}
cout<<l<<endl;
for(int i=0; i<n; i++, cout<<0<<endl)
for(int j=0; j<l and pos<m; j++)
cout<<a[pos++].S<<' ';
return 0;
}
