#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

#define FAST ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define mp make_pair
#define pb push_back
#define lp(i,s,f) for(ll i = s; i < ll(f); i++)
#define inF freopen("input.in", "r", stdin);
#define outF freopen("output.in", "w", stdout);
#define endl '\n'
#define MOD 1000000007
#define mm(arr) memset(arr, 0, sizeof(arr))
#define F first
#define S second

int main(){
    FAST
    int n, m, q;
    cin >> n >> m >> q;
    int rec[m];
    mm(rec);
    for(int i = 0; i < q; i++){
        int b;
        cin >> b;
        b--;
        rec[b] = 1;
    }
    vector<int> proj[n];
    int cnt[m];
    mm(cnt);
    bool ok[n];
    vector<int> ans;
    for(int i = 0; i < n; i++){
        int k; cin >> k;
        proj[i].resize(k);
        ok[i] = 1;
        for(int j = 0; j < k; j++){
            cin >> proj[i][j];
            proj[i][j]--;
            if(!rec[proj[i][j]]){
                ok[i] = 0;
            }
        }
        if(ok[i]){
            for(int j = 0; j < k; j++){
               cnt[proj[i][j]]++;
            }
        }
    }
    for(int i = 0; i < n; i++){
        bool has = 0;
        if(ok[i]){
            for(int j = 0; j < proj[i].size(); j++){
                if(cnt[proj[i][j]] == 1){
                    has = 1;
                    break;
                }
            }
        }
        if(has){
            ans.pb(i + 1);
        }
    }
    cout << ans.size() << endl;
    for(int i = 0; i < ans.size(); i++){
        cout << ans[i] << " ";
    }
    return 0;
}