#include <bits/stdc++.h>
using namespace std;
using i64 = int;
i64 const &N_ = 1e5 + 1;
i64 const &M_ = 1e6 + 1;
i64 N, D, M;
vector < i64 > ans[N_];
vector < pair < i64, i64 >> DAYS;
bool check(i64 machine) {
i64 d = 0;
i64 cnt = 0;
for (i64 i = 0; i < (i64) DAYS.size(); ) {
i64 j = i;
bool ok = false;
i64 val = max(DAYS[i].first, d + 1);
for (i64 cnt_ = 0; j < M and DAYS[j].first < val + 1 and DAYS[j].first >= val - D and cnt_ < machine; ++ cnt_, ++ j) {
// Let it be
cnt ++;
ok = true;
}
if (! ok) return false;
i = j;
d = val;
}
return cnt == M;
}
void get_ans(i64 machine) {
i64 d = 0;
for (i64 i = 0; i < (i64) DAYS.size(); ) {
i64 j = i;
bool ok = false;
i64 val = max(DAYS[i].first, d + 1);
for (i64 cnt_ = 0; j < M and DAYS[j].first < val + 1 and DAYS[j].first >= val - D and cnt_ < machine; ++ cnt_, ++ j) {
// Let it be
ans[val].push_back(DAYS[j].second);
ok = true;
}
if (! ok) return ;
i = j;
d = val;
}
}
void Solution() {
cin >> N >> D >> M;
for (i64 i = 0; i < M; ++ i) {
i64 a;
cin >> a;
DAYS.push_back(make_pair(a, i + 1));
}
i64 save = -1;
sort(DAYS.begin(), DAYS.end());
i64 l = 0, r = M;
while (l < r + 1) {
i64 mid = (l + r) / 2;
if (check(mid)) save = mid, r = mid - 1;
else l = mid + 1;
}
get_ans(save);
cout << save << endl;
for (i64 i = 1; i < N + 1; ++ i) {
for (auto it : ans[i]) {
cout << it << ' ';
}
cout << '0' << endl;
}
}
int main() {
Solution();
return 0;
}
