#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define F first
#define S second
using namespace std;
const ll N=1000006;
ll n, k, x, s, mx;
pair<int, int> a[N];
priority_queue<pair<int,int> > q;
int main(){ios_base::sync_with_stdio(false), cin.tie(0);
cin>>n>>k;
for(int i=0;i<n;i++)
cin>>x, s+=x,
mx=max(mx,x),
q.push({x,i+1});
if(s%k||k*mx>s){cout<<-1; return 0;}
cout<<s/k<<'\n';
while(!q.empty()){
cout<<1<<" ";
for(int i=0;i<k;i++)
a[i]=q.top(),
q.pop();
for(int i=0;i<k;i++){
if(a[i].F>1)q.push({a[i].F-1, a[i].S});
cout<<a[i].S<<" ";
}
cout<<'\n';
}
}
