#include <bits/extc++.h>
#include <bits/stdc++.h>
using namespace __gnu_pbds;
using namespace std;
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sz(x) (int)(x).size()
#define LSB(x) (x) & (-x)
#define fi first
#define se second
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
int N,D,M,ans=-1;
vector<vi> ans_v;
vector<pii> reqs;
void solve() {
cin>>N>>D>>M;
reqs.resize(M);
rep(i,0,M) cin>>reqs[i].fi,reqs[i].se=i;
sort(all(reqs));
int lb=1,ub=1000000;
while(lb<=ub) {
int mb=(lb+ub)/2;
queue<int> q;
vector<vi> curr(N+1);
bool v=1;
int k=0;
rep(i,1,N) {
for(;k<M&&reqs[k].fi==i;++k) q.push(k);
if(q.size()&&reqs[q.front()].fi+D<i) {
v=0;
break;
}
for(int j=0;j<mb&&q.size();++j) {
curr[i].push_back(reqs[q.front()].se+1);
q.pop();
}
}
v = v&(q.empty());
if(v) ans=mb,ans_v=curr,ub=mb-1;
else lb=mb+1;
}
cout<<ans<<'\n';
rep(i,1,N+1) {
for(auto j: ans_v[i]) cout<<j<<' ';
cout<<"0\n";
}
}
int main() {
//freopen("convention2.in", "r", stdin);
//freopen("convention2.out", "w", stdout);
cin.tie(0)->sync_with_stdio(0);
cin.exceptions(cin.failbit);
solve();
}
