#include <bits/stdc++.h>
using namespace std;
#define __Master_Moon__ int main()
#define ll long long
#define el "\n"
#define fi first
#define sq(x) (x)*(x)
#define se second
#define pub push_back
#define puf push_front
#define pii pair <int, int>
#define pll pair <long long, long long>
#define piii pair <int, pair <int, int>>
#define iiii pair <int, pair <int, pair <int, int>>>
#define plll pair <long long, pair <long long, long long>>
#define FOR(i, a, b) for(ll i = (a);i <=(b);i++)
#define FO(i, a, b) for(int i = (a);i >= (b);i--)
#define REP(i, n) for(int i = 0;i < (n);i++)
long const maxn = 1e6+5;
int n,m,k,ans;
pii a[maxn];
bool check(int val)
{
FOR(i,1,m)
{
int tmp = (i-1) / val + 1;
if(tmp - a[i].fi > k) return false;
}
return true;
}
void solve()
{
cin >> n >> k >> m;
FOR(i,1,m)
{
cin >> a[i].fi;
a[i].se = i;
}
sort(a+1,a+m+1);
int l = 1,r = m;
while(l<=r)
{
int mid = (l+r)/2;
if(n*mid >= m && check(mid))
{
ans = mid;
r = mid -1;
}
else l = mid + 1;
}
cout << ans << el;
REP(i,n)
{
int tmp = ans*i;
int j = tmp + 1;
while(j <= m && j <= tmp+ans)
{
cout << a[j].se << ' ';
j++;
}
cout << 0 << el;
}
}
__Master_Moon__
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
