#include <bits/stdc++.h>
#define ll long long
#define endl '\n'
#define all(a) a.begin(),a.end()
#define mod (ll)(10000007)
using namespace std;
const int mx = 1e6 + 15;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,d,m;
cin >> n >> d >> m;
vector<pair<int,int>> a(m);
for (int i=0;i<m;i++){
int x;
cin >> x;
a[i] = {x,i+1};
}
sort(all(a));
int s = 0,e=m;
int ans = m;
while (s<=e){
int mid = (s+e)/2;
int i = 0;
int day = 1;
while (i<m){
int up = upper_bound(all(a),make_pair(day,INT_MAX))-a.begin();
i = min(i+mid,up);
day++;
if (day==n+1) break;
}
if (i==m){
ans = mid;
e = mid - 1;
}
else s = mid + 1;
}
cout << ans << endl;
int cur = 0;
for (int i=1;i<=n;i++){
int up = upper_bound(all(a),make_pair(i,INT_MAX))-a.begin();
int t = cur+ans;
if (cur!=m){
for (;cur<min(t,up);cur++){
cout << a[cur].second << ' ';
}
}
cout << 0 << endl;
}
}
