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import java.io.IOException;
import java.io.InputStream;
import java.io.PrintStream;

public class eks {

	private static int skipWhitespace(final InputStream in) throws IOException {
		int val = -1;
		while ((val = in.read()) != -1) {
			if (!Character.isWhitespace((char) val))
				break;
		}

		return val;
	}

	private static int readInt(final InputStream in) {
		final StringBuilder b = new StringBuilder();
		try {
			int val = skipWhitespace(in);
			b.append((char) val);
			while ((val = in.read()) != -1) {
				if (Character.isWhitespace((char) val))
					break;
				b.append((char) val);
			}
			return Integer.parseInt(b.toString());
		} catch (final IOException e) {
			throw new RuntimeException(e);
		}
	}

	public void run(final InputStream in, PrintStream out) {
		int n = readInt(in);
		int m = readInt(in);
		int[] tl = new int[500];
		int[] tni = new int[500000];
		int cnt = 0;
		for (int i = 0; i < n; i++) {
			tl[i] = readInt(in);
			for (int k = 0; k < tl[i]; k++) {
				tni[cnt] = readInt(in);
				cnt++;
			}
		}
		int[] ts = new int[1000];
		for (int i = 0; i < m; i++) {
			int si = readInt(in);
			ts[i] = si;
		}

		if (cnt < m) {
			out.print(-1 + "\n");
			return;
		}
		
		for (int i = 0; i < cnt; i++) {
			if (tni[i] == ts[0]) {
				boolean res = true;
				int j;
				for (j = 1; j < m; j++) {
					if (tni[i + j] != ts[j]) {
						res = false;
						break;
					}
				}
				if (res) {
					int cpos = 0;
					int pos = i + j - 1;
					for (int k = 0; k < n; k++) {
						cpos += tl[k];
						if (cpos > pos) {
							out.print((k + 2) + "\n");
							return;
						}
					}
					break;
				}
			}
		}
		
		out.print(-1 + "\n");
	}

	public static void main(final String[] args) {
		new eks().run(System.in, System.out);
	}

}