1106

// Timus 1106

#include <iostream>
#include <vector>
#include <set>
#include <cmath>

#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()

// #define file_io
// #define many_tasks
#define int int32_t
#define ll int64_t

#define uint uint32_t
#define ull uint64_t

#define db double
#define ld long double


void ios() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
}

void dfs(std::vector<std::vector<int>> &g, std::vector<int> &color, int v) {
    if (color[v] == 0) color[v] = 1;
    for (auto &u : g[v]) {
        if (color[u] == 0) {
            color[u] = 3 - color[v];
            dfs(g, color, u);
        }
    }
}

//-----------------------------------------------------------------------------------------------//

void solve() {
    int n;
    std::cin >> n;
    std::vector<std::vector<int>> g(n);
    for (int i = 0; i < n; ++i) {
        int a;
        while (std::cin >> a) {
            if (a == 0) break;
            g[i].push_back(a - 1);
        }
    }
    std::vector<int> res;
    std::vector<int> color(n, 0);
    for (int i = 0; i < n; ++i) {
        if (color[i] == 0) {
            dfs(g, color, i);
        }
    }

    for (int i = 0; i < n; ++i) {
        if (color[i] == 1) {
            res.push_back(i + 1);
        } else if (color[i] == 0) {
            std::cout << 0;
            return;
        }
    }
    std::cout << res.size() << '\n';
    for (auto &elem : res) {
        std::cout << elem << ' ';
    }

}

//-----------------------------------------------------------------------------------------------//

int main() {
#ifdef file_io
    freopen("C:\\file_io\\input.txt", "r", stdin);
    freopen("C:\\file_io\\output.txt", "w", stdout);
#endif
    ios();
#ifdef many_tasks
    size_t t;
    std::cin >> t;
    while (t-- > 0) {
        solve();
    }
#else
    solve();
#endif
    return 0;
}