#include <iostream>
#include <fstream>
#include <vector>
#include <queue>

using namespace std;
vector <vector <int> > graph;
vector <bool> used;

void dfs (int i) {
    used[i] = true;
    for (int j = 0; j < graph[i].size(); ++j) {
            if (!used[graph[i][j]]) {
                dfs(graph[i][j]);
        }
    }
}

bool checkGraph (int n) {
    for (int i = 0; i < n; ++i) {
        if  (!used[i])
            return 0;
    }
    return 1;
}

int main(int argc, const char * argv[]) {
    ifstream fin("/Users/ilabockov/Desktop/xcode/SWIFT/SwiftBook/graphs/graphs/input.txt");
    ofstream fout("/Users/ilabockov/Desktop/xcode/SWIFT/SwiftBook/graphs/graphs/output.txt");
    int n;
    int maxTime (0), firstDomino;
    fin >> n;
    graph.resize(n);
    used.resize(n);
    for (int i = 0; i < n; ++i) {
        int m;
        fin >> m;
        for (int i = 0; i < m; ++i) {
            int buf;
            fin >> buf;
            graph[i].push_back(buf - 1);
        }
    }
    fin.close();

    dfs(0);
    for (int i = 0; i < n; ++i) {
        if (!used[i]) {
            fout << "impossible";
            fout.close();
            return 0;
        }
        used[i] = false;
    }

    int flag = 0;
    for (int i = 0; i < n; ++i) {
        int time = 0;
//        queue <int> myQueue;
//        if (!used[i]) {
//            myQueue.push(i);
//            used[i] = true;
//            while (!myQueue.empty()) {
//                int i = myQueue.front();
//                myQueue.pop();
//                for (int j = 0; j < graph[i].size(); ++j) {
//                    if (!used[graph[i][j]]) {
//                        myQueue.push(graph[i][j]);
//                        used[graph[i][j]] = true;
//                        time ++;
//                    } else time --;
//                }
//            }
//        }
        queue <int> myQueue;
        myQueue.push(i);
        used[i] = true;
        while (true) {
            queue <int> bufQueue;
            while (!myQueue.empty()) {
                int i = myQueue.front();
                myQueue.pop();
                for (int j = 0; j < graph[i].size(); ++j) {
                    if (!used[graph[i][j]]) {
                        bufQueue.push(graph[i][j]);
                        used[graph[i][j]] = true;
                    }
                }
            }
            if (bufQueue.empty()) {
                break;
            }
            time++;
            myQueue = bufQueue;
        }

        if (time >= maxTime && checkGraph(n)) {
            maxTime = time;
            firstDomino = i;
            flag = 1;
        }
        for (int i = 0; i < n; ++i) {
            used[i] = false;
        }
    }
    if (flag == 1) {
        fout << maxTime << endl << firstDomino + 1;
    } else {
        fout << "impossible";
    }
    fout.close();
    return 0;
}