#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
#define rep(i,n) for(int i=0; i<(n); i++)


vector<int> player_skills;
vector<int> player_times;


struct Room{
    int id;
    vector<int> players;
    int value_e;

    Room(int player_id){
        id = player_id;
        players = { id };
        value_e = 0;
    }

    int get_num_players() const { return players.size(); }

    pair<int,int> merge_in(Room another, int tick){
        value_e += another.value_e;
        for(int l : players) for(int r : another.players){
            value_e += tick - player_times[l];
            value_e += tick - player_times[r];
        }
        for(int r : another.players) players.push_back(r);
        return { id, another.id };
    }

    double receive_score(int player_id, int tick){
        double skill = player_skills[player_id];
        
        int min_skill = 100;
        int max_skill = 0;
        int min_tick = 1001001;
        for(auto a : players){
            min_skill = min(min_skill, player_skills[a]);
            max_skill = max(max_skill, player_skills[a]);
            min_tick = min(min_tick, player_times[a]);
        }
        if(min_skill <= skill && skill <= max_skill) return 1.0e100;
        double mid_skill = (min_skill + max_skill) / 2.0;
        tick -= min_tick;
        double w = pow((mid_skill - 50.0) / 50.0, 2.0) * 2.0 + 3.0;
        //double w = 4.0;

        double margin_ticks = 30.0;
        double margin_w = 0.0;
        if(tick >= margin_ticks) w += (log(tick / margin_ticks)) * 1.0;
        // if(tick >= margin_ticks) margin_w += (tick - margin_ticks) / 20;
        // if(tick >= margin_ticks) cerr << margin_w << endl;
        w += margin_w;

        double l = min<double>(min_skill, max_skill - w);
        double r = max<double>(max_skill, min_skill + w);

        auto skill_dist = abs(mid_skill - skill) / 100.0;
        return (l <= skill && skill <= r) ? (100.0 - skill_dist) : 0.0;
    }
};




int main(){

    vector<Room> rooms;

    int num_tick; cin >> num_tick;
    int max_room_size; cin >> max_room_size;

    int next_player_id = 1;
    player_skills.push_back(0);
    player_times.push_back(0);

    rep(tick_idx, num_tick){
        int num_enter; cin >> num_enter;
        vector<pair<int,int>> buf;

        rep(enter_idx, num_enter){
            int enter_id = next_player_id++;
            int player_skill; cin >> player_skill;
            player_skills.push_back(player_skill);
            player_times.push_back(tick_idx);
            
            int to_enter = -1;
            double receive_score_max = 0.0;
            rep(room_arr_idx, rooms.size()){
                auto receive_score = rooms[room_arr_idx].receive_score(enter_id, tick_idx);
                if(receive_score > receive_score_max){
                    to_enter = room_arr_idx;
                    receive_score_max = receive_score;
                }
            }

            if(to_enter == -1){
                rooms.emplace_back(enter_id);
            }
            else{
                buf.push_back(rooms[to_enter].merge_in(Room(enter_id), tick_idx));
                if(rooms[to_enter].players.size() >= max_room_size){
                    swap(rooms[to_enter], rooms.back());
                    rooms.pop_back();
                }
            }
        }

        cout << buf.size() << "\n";
        for(auto a : buf){
            cout << a.first << " " << a.second << "\n";
        }
        cout << flush;
    }
    return 0;
}




struct ios_do_not_sync {
    ios_do_not_sync() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} ios_do_not_sync_instance;