#include <bits/stdc++.h>
#define sz(x) ((int)x.size())
#define pii pair<int, int>
#define pli pair<ll, int>
#define ft first
#define sd second
#define MP make_pair
#define PB push_back
using namespace std;
typedef long long ll;
const int oo = 2e9;
const ll OO = 1e18;
const int N = 1000100;
set<pli, greater<pli> > st;
vector<vector<ll> > ans;
vector<ll> vc;
int n, k;
ll a[N];
void BAD(){
cout << -1;
exit(0);
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> k;
bool ok = 1;
for (int i = 0; i < n; i++){
cin >> a[i];
if (i > 0)
ok &= bool(a[i] == a[i - 1]);
}
if (ok){
int kl = k / __gcd(n, k);
if (a[0] % kl == 0){
int bd = kl * n;
for (int it = 0; it < bd; it += k){
vc.clear();
for (int lit = 0; lit < k; lit++){
int ps = (it + lit) % n;
vc.PB(ps);
}
ans.PB(vc);
}
cout << sz(ans) << '\n';
for (int it = 0; it < sz(ans); it++){
cout << a[0] / kl;
for (ll x : ans[it])
cout << " " << x + 1;
cout << '\n';
}
} else {
cout << -1;
}
return 0;
}
for (int i = 0; i < n; i++){
st.insert(MP(a[i], i));
}
for (ll po = 59; po >= 0; po--){
ll cur = (1ll << po);
while ((*st.begin()).ft > 0){
vc.clear();
vc.PB(cur);
bool was = 0;
for (int it = 0; it < k; it++){
pli cr = (*st.begin());
st.erase(st.begin());
if (cr.ft < cur) {
vc.PB(cr.sd);
was = 1;
break;
}
a[cr.sd] -= cur;
vc.PB(cr.sd);
}
if (was) {
for (int it = 1; it < sz(vc); it++){
int x = vc[it];
if (it < sz(vc) - 1)
a[x] += cur;
st.insert(MP(a[x], x));
}
break;
} else {
ans.PB(vc);
for (int it = 1; it < sz(vc); it++){
int x = vc[it];
st.insert(MP(a[x], x));
}
}
}
}
if ((*st.begin()).ft > 0)
BAD();
cout << sz(ans) << '\n';
for (int it = 0; it < sz(ans); it++){
// cout << "1";
for (int i = 0; i < sz(ans[it]); i++){
if (i == 0)
cout << ans[it][0];
else cout << " " << ans[it][i] + 1;
}
cout << '\n';
}
return 0;
}
