#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vl;
typedef pair<ll, ll> pl;
typedef long double ld;

#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define max(a, b) (a>b ? a : b)
#define min(a, b) (a<b ? a : b)
#define FAST ios::sync_with_stdio(0), cin.tie(0),cout.tie(0)


const int N = int(1e6) + 3;
const int MOD = int(1e9) + 7;

int n,m;
int q, a[N];
int w[N],x;
vector<int> p[N];
int cnt[N];
set<int> ss;
int main() {
    FAST;
    //freopen("easy", "r", stdin);
    cin >> n >> m;
    cin >> q;
    for(int i=0;i<q;i++){
        cin >> x;
        a[x]=1;
    }

    for(int i=0;i<n;i++){
        cin >>w[i];
        for(int j=0;j<w[i];j++){
            cin >> x;
            if(a[x]==0)
                continue;
            p[i].pb(x);
            cnt[x]++;
        }
    }
    for(int i=0;i<n;i++){
        if(p[i].size()!=w[i]){
            for(auto u:p[i]){
                cnt[u]--;
            }
        }
    }
    for(int i=0;i<n;i++){
        if(p[i].size()==w[i]){
            for(auto u:p[i]){
                if(cnt[u]==1){
                    ss.insert(i);
                }
            }
        }
    }
    cout << ss.size() << endl;
    for(auto u:ss){
        cout << u+1 << endl;
    }

    return 0;
}