#include <bits/stdc++.h>
typedef long long int ll;
#define endl            '\n'
#define pb             push_back
#define mp              make_pair
#define pll             pair<ll,ll> 
#define fill(x, y)     memset(x, y, sizeof(x))
#define all(x)         (x).begin(), (x).end()
#define debug(x)       { cerr << #x << " = " << x << endl; }
#define IO	       { ios_base::sync_with_stdio(false); cin.tie(0); }
#define read(x)	       freopen(x, "r", stdin)
#define write(x)       freopen(x, "w", stdout)
#define N       1000000

using namespace std;

typedef vector<int> vi;



struct DSU {
    vi Arr, sz;
 
    int root (int i)
    {
        while(Arr[ i ] != i)
        {
            Arr[i] = Arr[ Arr[i] ] ; 
            i=Arr[i]; 
        }
        return i;
    }
    
    DSU(int n)
    {
        Arr = vi(n+5);
        sz = vi(n+5);
        for(int i = 0;i<n;i++)
        {
            Arr[i] = i ;
            sz[i] = 1;
        }
    }
    
    void Union(int A,int B)
    {
        int root_A = root(A);
        int root_B = root(B);
        if(sz[root_A] < sz[root_B ])
        {
            Arr[ root_A ] = Arr[root_B];
            sz[root_B] += sz[root_A];
        }
        else
        {
            Arr[root_B] = Arr[root_A];
            sz[root_A] += sz[root_B];
        }
    
    }
 
};

void solve() {
    int n;
    cin >> n;
    map<int, vector<int>> mp;

    for (int i=1; i<=n; i++) {
        int m;
        cin >> m;
        for (int j=0; j<m; j++) {
            int x;
            cin >> x;
            mp[x].pb(i);
        }
    }
    DSU dsu(n+100);

    vector<vi> connects;

    for (auto &k: mp) {
        int col = k.first;
        for (int i=1; i<k.second.size(); i++) {
            // try to connect k.second[i] and k.second[i-1]
            if (dsu.root(k.second[i]) != dsu.root(k.second[i-1])) {
                dsu.Union(k.second[i], k.second[i-1]);
                connects.push_back({k.second[i], k.second[i-1], col});
            }
        }
    }
    if (connects.size() != n-1) {
        cout << "impossible" << endl;
    }
    else {
        for (vi x: connects) {
            cout << x[0] << " " << x[1] << " " << x[2] << endl;
        }
    }
}


int main() {
    IO;
    //cout << fixed << setprecision(10);
    solve();
}