#include<bits/stdc++.h>
using namespace std;
#define int long long 
#define endl '\n'
struct RES{
    int p,q,r;
};
vector<RES> res;
const int N = 400005;
vector<int> adj[N];
vector<int> ids[N];

int vis[N];
int parent[N];
int decompress[N];
int n;
void dfs(int u){
    vis[u] = 1;
    for(auto v:adj[u]){
        if( vis[v] ) continue;
        parent[v] = u;
        if( v <=n ) {
            res.push_back({parent[u],v,decompress[u-n]});
        }
        dfs(v);
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    
    cin>>n;
    set<int> st;
    for(int i=1;i<=n;i++){
        int t;
        cin>>t;
        for(int j=0;j<t;j++){
            int a;
            cin>>a;
            st.insert(a);
            ids[i].push_back(a);
        }
    }
    map<int,int> compress;
    int id = 1;
    for(auto s:st){
        compress[s] = id;
        decompress[id] = s;
        id++;
    }
    /*for(int i=1;i<=2*n;i++){
        cout<<i<<endl;
        for(auto v:adj[i]) cout<<v<<" ";
        cout<<endl;
    }*/
    for(int i=1;i<=n;i++){
        for(auto v:ids[i]){
            int j = compress[v];
            adj[i].push_back(j+n);
            adj[j+n].push_back(i);
        }
    }
   /* for(int i=1;i<=2*n;i++){
        cout<<i<<endl;
        for(auto v:adj[i]) cout<<v<<" ";
        cout<<endl;
    }*/

    dfs(1);
    //cout<<res.size()<<endl;
    if( res.size() != n-1 ){
        cout<<"impossible\n";
        return 0;
    }
    for(auto r:res) cout<<r.p<<" "<<r.q<<" "<<r.r<<endl;
    
}

/*
6
2 17 10
1 5
2 10 22
3 17 22 9
2 17 8
3 9 22 16
*/
/*
6
2 17 10
2 5 10
2 10 22
3 17 22 9
2 17 8
3 9 22 16
*/