#include<bits/stdc++.h>
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long int
const ll N = 100+5 , INF = 1e18 , MOD = 1e9+7;
void solve(){
ll n,d,m;
cin >> n >> d >> m;
vector<pair<ll,ll>> a(m+5);
for(ll i = 1; i <= m; i++){
cin >> a[i].first;
a[i].second = i;
}
sort(a.begin()+1,a.begin()+m+1);
ll low = ceil((double)m/(double)n) , high = m;
ll ans;
while(low <= high){
ll mid = (low+high)/2;
bool possible = true;
for(ll i = 1; i <= m; i++){
ll day = ceil((double)i/(double)mid);
if(day > a[i].first+d) possible = false;
}
if(possible){
ans = mid;
high = mid-1;
}
else low = mid+1;
}
cout << ans << "\n";
for(ll i = 1; i <= n; i++){
for(ll j = (i-1)*ans+1; j <= min(i*ans,m); j++){
cout << a[j].second << " ";
}
cout << "0\n";
}
}
int main(){
fast;
ll tc = 1;
// cin >> tc;
while(tc--) solve();
return 0;
}
