#include <bits/stdc++.h>

using namespace std;

#define PI 3.14159265358979323846
#define mod 1000000007
#define ll long long
#define vi vector<int>
#define ii pair<int, int>
#define pb push_back
#define all(c) (c).begin(), (c).end()

const int N = 1e6;

int n, m, q;
vi a, sureWin, ans;
vector<vi> x;
map<int, pair<bool, int>> k;
bool win[N + 1], sureLoss[N];

int main() {
// 	freopen("input.txt", "r", stdin);
// 	freopen("output.txt", "w", stdout);

	cin >> n >> m >> q;
	a.resize(q);
	for (int i = 0; i < q; ++i) {
		cin >> a[i];
		win[a[i]] = 1;
	}
	x.resize(n);
	for (int w, i = 0; i < n; ++i) {
		cin >> w;
		x[i].resize(w);
		for (int j = 0; j < w; ++j) {
			cin >> x[i][j];

			if (!win[x[i][j]])
				sureLoss[i] = 1;
		}
	}

	for (int i = 0; i < n; ++i) {
		if (!sureLoss[i]) {
			for (int j = 0; j < x[i].size(); ++j) {
				if (k.count(x[i][j])) {
					k[x[i][j]].first = false;
				}
				else {
					k.insert({x[i][j], {true, i}});
				}
			}
		}
	}

	for (auto it = k.begin(); it != k.end(); ++it) {
		if (it->second.first) {
			sureWin.pb(it->second.second);
		}
	}

	sort(sureWin.begin(), sureWin.end());
	if (!sureWin.empty())
		ans.pb(sureWin[0]);
	
	for (int i = 1; i < sureWin.size(); ++i) {
		if (sureWin[i] != sureWin[i - 1])
			ans.pb(sureWin[i]);
	}

	cout << ans.size() << endl;
	for (int i = 0; i < ans.size(); ++i)
		cout << ans[i] + 1 << " ";
}