#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
int n, k;
long long a[N];
int comp_num;
deque<pair<long long, int>> components[N / 1000];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k;
long long sum = 0, mx = 0;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
sum += a[i];
mx = max(mx, a[i]);
}
if (sum % k != 0 || mx > (sum / k))
{
cout << -1 << '\n';
return 0;
}
long long needSum = sum / k;
long long blockSum = 0;
for (int i = 1; i <= n; i++)
{
if (blockSum + a[i] <= needSum)
{
blockSum += a[i];
components[comp_num].push_back(make_pair(a[i], i));
}
else
{
a[i] -= needSum - blockSum;
blockSum = needSum;
i--;
}
if (blockSum == needSum)
{
comp_num++;
blockSum = 0;
}
}
vector<vector<long long>> ans;
while (sum)
{
long long min_sum = INT64_MAX;
for (int i = 0; i < comp_num; ++i)
{
assert(components[i].size());
min_sum = min(min_sum, components[i].front().first);
}
vector<long long> seq;
seq.push_back(min_sum);
for (int i = 0; i < comp_num; ++i)
{
assert(components[i].size());
seq.push_back(components[i].front().second);
components[i].front().first -= min_sum;
if (!components[i].front().first)
{
components[i].pop_front();
}
}
sum -= min_sum * comp_num;
ans.push_back(seq);
}
cout << ans.size() << '\n';
for (auto& i : ans)
{
for (auto j : i)
{
cout << j << " ";
}
cout << '\n';
}
return 0;
}
