#include<bits/stdc++.h>

using namespace std;

struct UnionFind {
  vector<int> data;
  UnionFind(int size) : data(size, -1) { }
  bool unionSet(int x, int y) {
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool findSet(int x, int y) {
    return root(x) == root(y);
  }
  int root(int x) {
    return data[x] < 0 ? x : data[x] = root(data[x]);
  }
  int size(int x) {
    return -data[root(x)];
  }
};

int main(){
  int T,R;
  cin >> T >> R;
  int p=0;
  UnionFind uf(5555);
  vector<int> S(5555);
  for(int i=0;i<T;i++){
    int n;
    cin >> n;
    vector<pair<int,int>> act;
    for(int j=0;j<n;j++){
      p++;
      cin >> S[p];
      for(int k=p-1;k>=1;k--){
        if(abs(S[k]-S[p])<=2 && uf.size(k)+uf.size(p)<=R){
          act.push_back({k,p});
          uf.unionSet(k,p);
        }
      }
    }
    cout << act.size() << '\n';
    for(auto &nx : act){cout << nx.first << ' ' << nx.second << '\n';}
    fflush(stdout);
  }
  return 0;
}