#pragma GCC optimize("O3")
#include <algorithm>
#include <array>
#include <bitset>
#include <iostream>
#include <numeric>
#include <vector>
#include <assert.h>
using namespace std;
#define rep(i,a,b) for(int i=(a); i<(b); ++i)
#define all(x) x.begin(),x.end()
#define sz(x) int(x.size())
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vi> vvi;

// to quickly check if element exists, we use bitset
const int N = 50000, B = 1000;
typedef bitset<N> bs;
bs vis[N]; 

int main(){
    cin.tie(NULL),cin.sync_with_stdio(false);
    
    int n; cin >> n;
    vvi a;
    vi inds, coords, tmp;
    rep(i,0,n){
        int k; cin >> k;
        vi v(k);
        for(auto& c : v) cin >> c;
        if (k<2) continue;
        
        a.push_back(v);
        inds.push_back(i);
        for(auto c : v) tmp.push_back(c);
    }

    n = sz(a);
    sort(all(tmp));
    rep(i,0,sz(tmp)-1) if ((!i or tmp[i-1] != tmp[i]) and tmp[i] == tmp[i+1]){
        coords.push_back(tmp[i]);
    }
    assert(coords.size()<=N);
    rep(i,0,n) {
        rep(j,0,sz(a[i])){
            auto it = lower_bound(all(coords), a[i][j]);
            if (it != end(coords) and *it == a[i][j]) {
                a[i][j] = it - begin(coords);
                vis[i][a[i][j]] = 1;
            }else{
                a[i][j] = a[i].back();
                a[i].pop_back();
                --j;
            }
        }
        sort(all(a[i]));
    }

    vi ord(n); iota(all(ord),0);
    stable_sort(all(ord),[&](int i, int j){ 
        return sz(a[i]) < sz(a[j]);
    });

    rep(ii,0,n) if (sz(a[ord[ii]])>1) rep(jj,max(ii+1,n-B-1),n){
        int i = ord[ii], j = ord[jj];
        int frst = -1;
        for(auto v : a[i]) {
            if (vis[j][v]){
                if (frst<0) frst = v;
                else{
                    // solution found!
                    cerr << "FIRST\n";
                    cout << coords[frst] << ' ' << coords[v] << ' ' << inds[i]+1 << ' ' << inds[j]+1  << '\n';
                    exit(0);
                }
            }
        }
    }

    typedef unsigned short us;
    vector<array<us,3>> pairs;
    pairs.reserve((51000/B)*51000);
    rep(ii,0,n-B){
        int i = ord[ii];
        rep(j,0,sz(a[i])) rep(k,j+1,sz(a[i])){
            pairs.push_back({ (us) a[i][j], (us) a[i][k], (us) i});
        }
    }

    sort(all(pairs));
    rep(i,0,sz(pairs)-1){
        if (pairs[i][0] == pairs[i+1][0] and pairs[i][1] == pairs[i+1][1]){
            cerr << "SECOND\n";
            cout << coords[pairs[i][0]] << ' ' << coords[pairs[i][1]] << ' ' << inds[pairs[i][2]]+1 << ' ' << inds[pairs[i+1][2]]+1 << '\n';
            exit(0);
        }
    }

    cout << "impossible\n";
}