#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 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;
	vector<priority_queue<int, vector<int>, greater<int>>> que(20);
	vector<int> size(20, 0);
	int cnt = 1;
	FOR(t,0,T){
		int N;
		cin >> N;
		FOR(i,0,N){
			int s;
			cin >> s;
			if(s == 100)  s--;
			que[s / 5].push(cnt++);
		}
		vector<P> ans;
		FOR(q,0,20){
			while((int)que[q].size() >= 2){
				int a = que[q].top();
				que[q].pop();
				int b = que[q].top();
				que[q].pop();
				ans.push_back({a, b});
				size[q] += 2;
				if(size[q] == 4){
					size[q] = 0;
				}else{
					que[q].push(a);
					--size[q];
				}
			}
		}
		cout << ans.size() << endl;
		for(auto p: ans){
			cout << p.first << " " << p.second << endl;
		}
	}

	return 0;
}