#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int N;
	cin>>N;
	
	vector<map<int,int>> mp(N);
	map<int,int> LCA;
	rep(i,N){
		int m;
		cin>>m;
		
		rep(j,m){
			int p,e;
			cin>>p>>e;
			mp[i][p] = e;
			LCA[p] = max(LCA[p],e);
		}
	}
	
	map<int,int> pos;
	int cur = 0;
	vector<int> ps(LCA.size());
	for(auto a:LCA){
		pos[a.first] = cur;
		ps[cur] = a.first;
		cur++;
	}

	
	set<vector<int>> S;
	
	rep(i,N){
		vector<int> t;
		for(auto a:mp[i]){
			if(a.second == LCA[a.first]){
				//cout<<pos[a.first]<<endl;
				t.push_back(pos[a.first]);
			}
		}
		sort(t.begin(),t.end());

		if(S.count(t))continue;
		//cout<<i<<endl;
		rep(j,1<<t.size()){
			vector<int> nt;
			rep(k,t.size()){
				if((j>>k)&1)nt.push_back(t[k]);
			}
			S.insert(nt);
		}
		/*
		for(auto a:S){
			rep(j,a.size()){
				cout<<a[j]<<',';
			}
			cout<<endl;
		}
		cout<<endl;
		*/
	}
	//cout<<'a'<<endl;
	
	vector<vector<int>> t(cur);
	
	rep(i,cur)t[i] = {i};
	
	while(true){
		if(t.size()==0){
			cout<<-1<<endl;
			return 0;
		}
		vector<vector<int>> nt;
		rep(i,t.size()){
			
			int last = t[i].back();
			for(int j=last+1;j<cur;j++){
				vector<int> temp = t[i];
				temp.push_back(j);
				if(!S.count(temp)){
					cout<<temp.size()<<endl;
					
					vector<vector<int>> ans(temp.size());
					rep(i,N){
						rep(j,temp.size()){
							if(mp[i].count(ps[temp[j]])&&mp[i][ps[temp[j]]]==LCA[ps[temp[j]]])continue;
							ans[j].push_back(i+1);
							break;
						}
					}
					
					rep(i,temp.size()){
						rep(j,ans[i].size()){
							if(j!=0)cout<<' ';
							cout<<ans[i][j];
						}
						cout<<endl;
					}
					
					
					return 0;
				}
				nt.push_back(temp);
				
			}
		}
		swap(t,nt);
		
	}
	
	return 0;
}