#include<bits/stdc++.h>
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
*/
using namespace std;
#pragma GCC optimize ("unroll-loops,Ofast,O3")
#pragma GCC target("avx,avx2,fma")
#define F first
#define S second
#define int long long
#define sz(x) (int)x.size()
#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define NFS ios_base::sync_with_stdio(0) , cin.tie(0) , cout.tie(0) ;
#define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)
//#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
typedef long long ll;
const int E = 1e6+777;
const long long inf = 1e18+777;
const int N = 1e5+777;
const int MOD = 1e9+7;
int n, k, a[E], sum;
vector<vector<int>> res;
priority_queue<pair<int,int>> pq;
signed main(){auto solve=[&](){
cin >> n >> k;
for(int i = 1; i <= n; ++i){
cin >> a[i];
sum += a[i];
if(a[i] > 0){
pq.push({a[i], i});
}
}
bool ok = (sum % k == 0);
for(int i = 1; i <= n; ++i){
if(a[i] > sum / k) ok = false;
}
if(!ok){
cout << -1;
return;
}
int len = sum / k;
vector<vector<pair<int,int>>> m(k);
vector<int> sm(k, 0), u(k, 0);
for(int i = 1, e = 0; i <= n;){
if(sm[e] + a[i] <= len){
m[e].pb({a[i], i});
sm[e] += a[i];
++i;
}else{
int cur = len - sm[e];
if(!cur){
++e;
continue;
}
sm[e] += cur;
m[e].pb({cur, i});
a[i] -= cur;
++e;
}
if(!a[i])++i;
}
// cerr << "M\n";
// for(int i = 0; i < k; ++i){
// for(int j = 0; j < sz(m[i]); ++j){
// cerr << m[i][j].F << ' ';
// }
// cerr << '\n';
// }cerr << '\n';
auto check = [&](){
bool ok = 0;
for(int i = 0; i < k; ++i){
if(sm[i])ok=1;
}
return ok;
};
while(check()){
// cerr << "OK\n";
vector<int> r;
int mn = LLONG_MAX;
for(int i = 0; i < k; ++i){
mn = min(mn, m[i][u[i]].F);
}
r.pb(mn);
for(int i = 0; i < k; ++i){
sm[i] -= mn;
m[i][u[i]].F -= mn;
r.pb(m[i][u[i]].S);
if(m[i][u[i]].F == 0){
++u[i];
}
}
res.pb(r);
}
cout << sz(res) << '\n';
for(auto v : res){
for(auto it : v)
cout << it << ' ';
cout << '\n';
}
};NFS;solve();}
