#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

	int n;
	cin >> n;

	vector<vector<int>> csucsok(n, vector<int>());
	vector<int> fok(n, 0);
	for(int i = 0; i < n; i++){
		while(1){
			int a;
			cin >> a;

			if(a == 0) break;

			a--;
			csucsok[i].push_back(a);
			fok[i]++;
		}
	}

	vector<bool> kettes(n, 0);
	int db = 0;
	queue<int> bejar;
	for(int i = 0; i < n; i++) bejar.push(i);

    while(!bejar.empty()){
        int i = bejar.front();
        bejar.pop();

        if(fok[i] >= 2){
            if(kettes[i]){
                kettes[i] = 0;
                db--;
            } else{
                kettes[i] = 1;
                db++;
            }

            for(int x : csucsok[i]){
                if(kettes[x] == kettes[i]){
                    fok[i]++;
                    fok[x]++;
                    bejar.push(x);
                } else{
                    fok[i]--;
                    fok[x]--;
                }
            }
        }
    }

	cout << db << "\n";
	for(int i = 0; i < n; i++){
		if(kettes[i]){
			cout << i + 1 << " ";
		}
	}
	cout << "\n";
}