#include <bits/stdc++.h>
using namespace std;
#define sz(x) (int)(x).size()
#define rep(i, l, r) for (int i = l; i < (r); i++)
#define all(x) begin(x), end(x)
#define endl "\n"

typedef long long ll;
typedef vector<int> vi;
typedef vector<pair<int, int>> vii;

template<class T> void out(T x) { cout << x << '\n'; }
template<class T> void out(vector<T> x) { for (int i = 0; i < sz(x); i++) cout << x[i] << " \n"[i == sz(x) - 1]; }
template<class T> void chmax(T &a, T x) {a = max(a, x);}


struct dsu {
    int n;
    vi par;
    dsu(int n) : n(n) {
        par = vi(n, -1);
    }

    int leader(int x) {
        if (par[x] < 0)return x;
        return par[x] = leader(par[x]);
    }

    int merge(int x, int y) {
        x = leader(x), y = leader(y);

        par[y] += par[x];
        par[y] = x;
        return x;
    }
    bool same(int x, int y) {
        return leader(x) == leader(y);
    }
};

void solve(){
    int n;cin >> n;

    map<int, vector<int>> s;
    rep(i, 0, n) {
        int k;cin >> k;
        while (k--){
            int k;cin >> k;s[k].emplace_back(i);
        }
    }
    dsu uf(n);
    vector<array<int, 3>> ans;
    for (auto [x, v] : s) {
        int f = v.front();
        for(auto g: v) {
            if (!uf.same(f, g))ans.emplace_back(array<int, 3>{f, g, x}), uf.merge(f, g);
        }
    }

    if (sz(ans) < n - 1)cout << "impossible" << endl;
    else for (auto [f, g, x] : ans) cout << f + 1 << " " << g + 1 << " " << x << endl;
}

int main() {
    int T = 1;
    while (T--)solve();
}