#include <bits/stdc++.h>
#pragma GCC diagnostic ignored "-Wunused-result"
#define int long long
using namespace std;
const int maxVerrous = 1000*1000;
int nbVerrous, tailleOperation;
int reqUnlock[maxVerrous];
int cur[maxVerrous];
priority_queue<pair<int, int>> prq;
signed main()
{
scanf("%lld%lld", &nbVerrous, &tailleOperation);
int som = 0, mx = 0;
for (int indVerrou = 0; indVerrou < nbVerrous; ++indVerrou) {
scanf("%lld", &reqUnlock[indVerrou]);
som += reqUnlock[indVerrou];
mx = max(mx, reqUnlock[indVerrou]);
prq.push({reqUnlock[indVerrou], indVerrou});
}
if (som % tailleOperation != 0 || mx > som / tailleOperation) {
printf("-1\n");
return 0;
}
vector<vector<int>> operations;
operations.reserve(100*1000);
vector<int> curOp(tailleOperation + 1);
int red = som / tailleOperation;
while (! prq.empty()) {
int nbRestants = prq.size();
if (nbRestants < tailleOperation) {
printf("-1\n");
return 0;
}
stack<int> remise;
int x = LLONG_MAX;
for (int indPris = 1; indPris <= tailleOperation; ++indPris) {
auto e = prq.top();
prq.pop();
curOp[indPris] = e.second;
x = min(x, e.first);
remise.push(e.second);
}
if (! prq.empty()) {
x = min(x, red - prq.top().first);
}
curOp[0] = x-1;
red -= x;
operations.push_back(curOp);
while (! remise.empty()) {
int ld = remise.top();
cur[ld] += x;
if (reqUnlock[ld] - cur[ld] != 0) {
prq.push({reqUnlock[ld] - cur[ld], ld});
}
remise.pop();
}
}
printf("%lld\n", (int)(operations.size()));
for (auto op : operations) {
for (int choisi : op) {
printf("%lld ", choisi+1);
}
printf("\n");
}
return 0;
}
