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

typedef long long ll;
#define int ll


#define lp3(i,s,n) for(int i = s;i < int(n); ++i)
#define lp(i, n) lp3(i,0,n)
#define pb push_back
#define debug(x) cout<<"[" << #x << " is: " << x << "] "<<endl;

#define file freopen("input.in","r",stdin);
#define fastIO std::ios::sync_with_stdio(false); cin.tie(0);


void solve(){
    int n, m;
    cin>>n>>m;
    vector<bool> v(m+10);
    int q; cin>>q;
    while(q--){
        int x; cin>>x;
        v[x-1] = true; 
    }

    vector<bool> maybe(n+10);
    vector<vector<int>> person(m+10);
    vector<bool> done(m+10);
    vector<vector<int>> project(n+10);
    lp(i, n){
        int w; cin>>w;
        bool isok = true;
        while(w--){
            int x; cin>>x;
            if(!v[x-1]) isok = false;
            person[x-1].push_back(i);
            project[i].push_back(x-1);
        }
        if(isok) maybe[i] = true;
    }

    vector<int> ans;
    lp(i, n){
        if(maybe[i]){
            bool found = false;
            for(int x: project[i]){
                if(done[x])
                    continue;
                bool may = false;
                for(int y: person[x]){
                    if(y == i)
                        continue;
                    if(maybe[y]){
                        may = true;
                        break;
                    }
                }
                if(!may){
                    found = true;
                    break;
                }
                done[x] = true;
            }
            if(found) ans.push_back(i+1);
        }
    }

    cout<<ans.size()<<endl;
    for(int i = 0; i < ans.size(); i++){
        if(i != 0) cout<< " ";
        cout<<ans[i];
    }
    if(ans.size())
        cout<<endl;
}

int32_t main() {  fastIO
    
    int t = 1; //cin>>t;
    while(t--){
        solve();
    }
    
    return 0;
}