#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <fstream>
#include <stack>
#include <map>
#include <cstring>
#include <cmath>
#include <set>
#include <iterator>
#include <cmath>
#include <locale>
#include <queue>
#include<deque>
#include <stack>


using namespace std;



const int MOD = 1e9+7;



int main()
{
    int N = 0, a = 0, m = 0,k = 0 ,t = 0, mi =-1;
    cin >> N;
    vector<stack<int> > s(N);
    for(auto i = 0; i < N; ++i)
    {
        while(!s[i].empty())
        {
            s[i].pop();
        }
    }
    if (N == 0)
        return 0;
    vector<pair<int, int> > answ;
    for(auto i = 0; i < N; ++i)
    {
        cin >> m;
        if (m != 0)
        {
            for(auto j = 0; j < m; ++j)
            {
                cin >> a;
                if(a == i + 1)
                    k++;
                s[i].push(a);
                t++;
            }
        }
    }
    if(k == t || N == 1)
        return 0;
    t = 0;
    k = 0;
    if (N == 2)
    {
        while(!s[1].empty())
        {
            s[0].push(s[1].top());
            s[1].pop();
            answ.push_back(make_pair(2, 1));
        }
        while (!s[0].empty())
        {
            t++;
            a = s[0].top();
            s[0].pop();
            s[1].push(a);
            if (a != 1)
                answ.push_back(make_pair(1, 2));
            if (t == 1)
            {
                mi = a;
            }
           // cout << mi << " fgsasg  " << a << endl;
            if (t > 1)
            {
                if (a > mi)
                {
                    cout << 0;
                    return 0;
                }
                if (mi > a)
                    mi = a;
            }
        }
    }

    if (N > 2)
    {
        for (int i = 1; i < s.size() ; ++i)
        {
            while(!s[i].empty())
            {
                a = s[i].top();
                s[i].pop();
                s[0].push(a);
                answ.push_back(make_pair(i + 1, 1));
                //cout << s[0].top() << endl;
            }
        }
        while(!s[0].empty())
        {
            a = s[0].top();
            s[0].pop();
            if (a == 1)
            {
                s[N - 1].push(a);
                answ.push_back(make_pair(1, N));
            }
            else{
                s[a - 1].push(a);
                answ.push_back(make_pair(1, a));
            }
        }
        while(!s[N - 1].empty())
        {
            a = s[N - 1].top();
            s[N - 1].pop();
            if (a == 1){
                s[0].push(a);
                answ.push_back(make_pair(N, 1));
            }
            else{
                s[N - 2].push(a);
              //  cout << a << "  " << endl;
                answ.push_back(make_pair(N, N - 1));
            }
            if (s[N - 1].size() == 0)
                break;
        }
        if (s[N - 2].size() > 0)
            a = s[N - 2].top();
            while(a == N)
            {
                s[N - 2].pop();
                s[N - 1].push(a);
                //cout << a << " dasdoajod" << endl;
                answ.push_back(make_pair(N - 1, N));
                if (s[N - 2].size() == 0)
                    break;
                a = s[N - 2].top();
            }
    }







    for(int i = 0; i < answ.size(); ++i)
    {
       cout << answ[i].first << " " << answ[i].second << endl;
    }


    return 0;
}