#include<bits/stdc++.h>
#ifndef LOCAL
#define cerr if(false)cerr
#endif // LOCAL
using namespace std;
using ll = long long;
const int N = 1e6 + 66;
pair<ll,int>a[N];
vector<vector<int>>ans;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int n, k;
cin >> n >> k;
for (int i = 1 ; i <= n ; ++ i) {
cin >> a[i].first; a[i].second = i;
}
bool ok = 1;
while (1) {
sort(a + 1, a + 1 + n);
reverse(a + 1, a + 1 + n);
if (a[1].first == 0) break;
ans.push_back(vector<int>(k));
for (int i = 1 ; i <= k ; ++ i) {
if (a[i].first <= 0) {
ok = 0;
break;
}
a[i].first--;
ans.back()[i - 1] = a[i].second;
}
}
if (ok == 0) {
cout << "-1";
return 0;
}
cout << ans.size() << "\n";
for (auto vec : ans) {
cout << "1 ";
for (int i : vec) cout << i << " ";
cout << "\n";
}
}
