#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define ff first
#define ss second
#define ln "\n"
#define mp make_pair
const ll INF = 2e18;
const ll MOD = 1e9+7;
void solve(){
ll n, k; cin >> n >> k;
vector<pair<ll, ll>> a(n);
ll sum=0;
for (ll i=0; i<n; i++){
cin >> a[i].ff; a[i].ss=i;
sum+=a[i].ff;
}
sort(a.begin(), a.end());
if (a.back().ff>sum-a.back().ff or sum%k){
cout << -1 << ln; return;
}
vector<ll> divider;
ll op_cnt = sum/k, cur=0;
for (ll i=0; i<n; i++){
cur+=a[i].ff;
cur%=op_cnt;
if (cur) divider.push_back(cur);
}
sort(divider.begin(), divider.end());
divider.erase(unique(divider.begin(), divider.end()), divider.end());
divider.push_back(op_cnt);
vector<vector<ll>> opera(divider.size());
cur=0; ll opi=0;
for (ll i=0; i<n; i++){
while (opi<(ll)divider.size() and divider[opi]<=min(op_cnt, cur+a[i].ff)){
opera[opi].push_back(a[i].ss);
opi++;
}
if (cur+a[i].ff<op_cnt){
cur+=a[i].ff; continue;
}else{
a[i].ff=cur+a[i].ff-op_cnt;
i--;
cur=0; opi=0;
}
}
cout << opera.size() << ln;
for (ll i=0; i<(ll)opera.size(); i++){
cout << divider[i]-(i?divider[i-1]:0) << " ";
for (ll j=0; j<k; j++) cout << opera[i][j]+1 << " ";
cout << ln;
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
auto start = chrono::high_resolution_clock::now();
ll t=1;
// cin >> t;
while (t--) solve();
#ifdef LOCAL
auto duration = chrono::duration_cast<chrono::microseconds>(chrono::high_resolution_clock::now() - start);
cout << setprecision(0) << fixed << "time: " << (double)duration.count()/1000.0 << " milliseconds" << endl;
#endif
}
