This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define st string
#define fr first
#define se second
const ll mod=1e9+7;
using namespace std;
pair<ll, ll> a[1000100];
vector<pair<ll, vector<ll> > > v;
int main()
{
    //freopen("1.txt", "r", stdin);
    //freopen("1.txt", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    ll n, k;
    cin>>n>>k;
    for(ll i=1; i<=n; i++)
    {
        cin>>a[i].fr;
        a[i].se=i;
    }
    sort(a+1, a+1+n);
    while(a[n].fr)
    {
        vector<ll> q;
        /*for(ll i=1; i<=n; i++)
            cout<<a[i].fr<<" ";
        cout<<endl;*/
        if(!a[n-k+1].fr)
        {
            cout<<-1;
            return 0;
        }
        for(ll j=n; j>=n-k+1; j--)
        {
            q.push_back(a[j].se);
            a[j].fr--;
        }
        v.push_back({1, q});
        sort(a+1, a+1+n);
    }
    cout<<v.size()<<endl;
    for(ll i=0; i<v.size(); i++)
    {
        cout<<v[i].fr<<" ";
        for(ll j=0; j<v[i].se.size(); j++)
        {
            cout<<v[i].se[j]<<" ";
        }
        cout<<endl;
    }
    return 0;
}
/*
*/
Compilation message (stderr)
nicegift.cpp: In function 'int main()':
nicegift.cpp:59:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll i=0; i<v.size(); i++)
                 ~^~~~~~~~~
nicegift.cpp:62:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(ll j=0; j<v[i].se.size(); j++)
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