#include<bits/stdc++.h>
using namespace std;
#define int long long
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)
const int MX = 2e5+5;
const int INF = 1e17;
signed main()
{
fast();
int n, k; cin >> n >> k;
set<in> S;
vector<vector<int>> op;
for(int i = 1; i <= n; i++)
{
int x; cin >> x;
S.insert({x, i});
}
bool can = true;
while(S.size())
{
if(S.size() < k)
{
can = false;
break;
}
vector<in> readd;
vector<int> stuff;
for(int i = 1; i <= k; i++)
{
auto [X, g] = *prev(S.end());
if(X >= 2)
readd.pb({X-1, g});
stuff.pb(g);
S.erase(prev(S.end()));
}
op.pb(stuff);
for(auto pp: readd)
S.insert(pp);
}
if(!can)
{
cout << "-1\n";
return 0;
}
cout << op.size() << "\n";
for(auto v: op)
{
cout << "1 ";
for(auto x: v)
cout << x << " ";
cout << "\n";
}
return 0;
}
