// @EXPECTED_RESULTS@: RUN_TIME_ERROR, TIME_LIMIT_EXCEEDED, WRONG_ANSWER
#pragma GCC optimize("Ofast")
#include <iostream>
#include <map>
#include <vector>
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;

int main(){
    cin.tie(NULL),ios::sync_with_stdio(false);
    
    int n; cin >> n;
    map<pair<int,int>,int> mp;
    rep(it,1,n+1){
        int m; cin >> m; vi v(m);
        for(auto& c : v) cin >> c;
        if (m <= 1000 or n < 10000) for(auto i : v) {
            for(auto j : v) if (i<j){
                auto& at = mp[{i,j}];
                if (at > 0 and at != it){
                    cout << i << ' ' << j << ' ' << at << ' ' << it << '\n';
                    exit(0);
                } at = it;
            }   
        }
    }
    cout << "impossible\n";
}