#include <bits/stdc++.h>

using namespace std;

int n;
vector<int> graph [101];
bool used[101];
int len[101];

void bfs(int v){
    len[v]=1;
    used[v]=true;
    queue<int>q;
    q.push(v);
    while(!q.empty()){
        v=q.front();
        q.pop();
        for (int i=0; i<graph[v].size();++i){
            int to=graph[v][i];
            if (!used[to]){
                used[to]=true;
                len[to]=(len[v]+1)%2;
            }
        }
    }
}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cin >> n;
    for (int i=1; i<=n; ++i){
        int a;
        while (cin >> a && a!=0){
            graph[i].push_back(a);
        }
    }
    bool ok=true;
    for (int i =1; i<=n; ++i){
        if (graph[i].empty()){
            ok=false;
        }
    }
    if (ok) {
        vector<int>ans;
        int cnt=0;
        for (int i = 1; i <= n; ++i) {
            if (!used[i]) {
                bfs(i);
            }
        }
        for (int i=1; i<=n; ++i){
            if (len[i]==0){
                cnt++;
                ans.push_back(i);
            }
        }
        cout << cnt << '\n';
        for (auto elem: ans){
            cout << elem << " ";
        }
    }
    else{
        cout << 0;
    }
    return 0;
}