#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef long double ld;
#define FOR(i, a, b) for (int i = a; i < (b); i++)
#define RFOR(i, a, b) for (int i = a; i >= (b); i--)
#define range(a) a.begin(), a.end()
#define endl "\n"
#define Yes() cout << "Yes" << endl
#define No() cout << "No" << endl
#define MP make_pair
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, -1, 0, 1};
using P = pair<int, int>;
const long long INF = 1LL<<60;
void chmin(long long &a, long long b) { if (a > b) a = b; }
void chmax(long long &a, long long b) { if (a < b) a = b; }

int main(void){
	ios::sync_with_stdio(0);
	cin.tie(0);
	int T, R;
	cin >> T >> R;
	queue<int> que;
	int cnt = 1;
	FOR(t,0,T){
		int N;
		cin >> N;
		FOR(i,0,N){
			int s;
			cin >> s;
			que.push(cnt++);
		}
		cout << ((int)que.size() / 4) * 3 << endl;
		while((int)que.size() >= R){
			vector<int> a(4);
			FOR(i,0,4){
				a[i] = que.front();
				que.pop();
			}
			FOR(i,1,4){
				cout << a[0] << " " << a[i] << endl;
			}
		}
	}


	return 0;
}