#include <bits/stdc++.h> #define ll long long using namespace std; const int N=1e6+1; int main(){ cin.tie(NULL); cout.tie(NULL); ios_base::sync_with_stdio(false); ll n,k; cin>>n>>k; vector<ll> a(n+1); vector<queue<pair<ll,int>>> mas;ll dt=0ll; vector<pair<ll,vector<int>>> answ; ll sum=0ll; for(int i=1;i<=n;++i){ cin>>a[i]; sum+=a[i]; } if(sum%k!=0){ cout<<-1<<'\n'; return 0; } sum/=k; for(int i=1;i<=n;++i){ if(a[i]>sum){ cout<<-1<<'\n'; return 0; } } queue<pair<ll,int>> res; for(int i=1;i<=n;++i){ if((dt+a[i])==sum){ res.push({a[i],i}); mas.push_back(res); dt=0; while(!res.empty()){ res.pop(); } } else if(dt+a[i]>sum){ res.push({sum-dt,i}); mas.push_back(res); while(!res.empty()){ res.pop(); } res.push({a[i]-sum+dt,i}); dt=a[i]-sum+dt; } else{ res.push({a[i],i}); dt+=a[i]; } } while(!mas[0].empty()){ ll mn=1e18; for(auto i:mas){ ll g=i.front().first; mn=min(mn,g); } answ.push_back({mn,{}}); for(int i=0;i<int(mas.size());++i){ mas[i].front().first-=mn; answ.back().second.push_back(mas[i].front().second); if(mas[i].front().first==0){ mas[i].pop(); } } } cout<<answ.size()<<'\n'; for(auto i:answ){ cout<<i.first<<" "; for(auto j:i.second){ cout<<j<<" "; } cout<<'\n'; } return 0; }