#include "bits/stdc++.h"
using namespace std;
#define SZ(s) (int)s.size()
#define ff first
#define ss second
#define ll long long
int main(){
ios::sync_with_stdio(false); cin.tie(nullptr);
int n, k;
cin >> n >> k;
ll sm = 0, mx = 0;
vector <ll> a(n+1);
for(int i = 1; i <= n; i++){
cin >> a[i];
sm += a[i];
mx = max(a[i], mx);
}
if(sm % k != 0 or mx > (sm/k)){
cout << -1;
return 0;
}
queue <pair<ll,int>> q[k+1];
int ind = 1, x = 1;
ll s = 0, sk = sm/k;
while(ind <= n){
ll y = min(sk-s,a[ind]);
q[x].push({y,ind});
s += y;
a[ind] -= y;
if(a[ind] == 0) ind++;
if(s == sk) x++, s = 0;
}
vector <ll> v;
while(!q[1].empty()){
ll mn = 1e18;
for(int i = 1; i <= k; i++){
mn = min(mn, q[i].front().ff);
}
v.push_back(mn);
for(int i = 1; i <= k; i++){
v.push_back(q[i].front().ss);
q[i].front().ff -= mn;
if(q[i].front().ff == 0) q[i].pop();
}
}
cout << SZ(v)/(k+1) << '\n';
int cnt = 0;
for(auto i : v){
cout << i << ' ';
if(++cnt == k+1){
cnt = 0;
cout << '\n';
}
}
return 0;
}
