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import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.*;

public class eks {

//	static parse(int[][] grammar, int[] word, int n) {
//		int r = n;
//		boolean[][][] P = new boolean[n][n][r];
//		for (int i = 0; i < n; i++) {
//			for (int j = 0; j < grammar.length; j++) {
//				P[0][i][j] = true;
//			}
//		}
//		for (int i = 1; i < n; i++) {
//			for (int j = 0; j < n-i+1; i++) {
//				for (int k = 0; k < i-1; k++) {
//					for (int[] production : grammar) {
//
//					}
//				}
//			}
//		}
//	}

	static String in1 = "3 2\n2 2 3\n3 1 3 3\n2 1 2\n3 1\n";

	static InputStream stringToStream(String string) {
		return new ByteArrayInputStream(string.getBytes(StandardCharsets.UTF_8));
	}

	public static void main(String[] args) {
		InputReader2 in = new InputReader2(System.in);
//		InputReader2 in = new InputReader2(stringToStream(in1));
		OutputWriter2 out = new OutputWriter2(System.out);

		int n = in.readInt();
		int m = in.readInt();

		int[][] grammar = new int[n][];
		int[] word = new int[m];

		for (int i = 0; i < n; i++) {
			int length = in.readInt();
			grammar[i] = new int[length];
			for (int j = 0; j < length; j++) {
				grammar[i][j] = in.readInt()-1;
			}
		}

		for (int i = 0; i < m; i++) {
			word[i] = in.readInt()-1;
		}

		List<Integer> cell = new LinkedList<>();
		cell.add(0);

		out.print(simulate(grammar, word, cell));
		out.flush();
		out.close();
	}

	static int simulate(int[][] grammar, int[] word, List<Integer> cell) {
		int counter = 0;
//		System.out.println("word: " + Arrays.toString(word));

		for (int i = 0; i < 18; i++) {
			counter++;
			if (findInSequence(word, cell) >= 0) return counter;
			Iterator<Integer> iterator = cell.iterator();
			List<Integer> newCell = new LinkedList<>();
			while (iterator.hasNext()) {
				int from = iterator.next();
				for (int k = 0; k < grammar[from].length; k++) {
					newCell.add(grammar[from][k]);
				}
			}
			cell = newCell;
//			System.out.println(cell);
		}
		return -1;
	}

	static int findInSequence(int[] signal, List<Integer> sequence) {
		int sequenceSize = sequence.size();
		if (signal.length > sequenceSize) return -1;
		int counter = 0;
		boolean match = false;
		int matchCounter = 0;
		Iterator<Integer> iterator = sequence.iterator();
		while (iterator.hasNext()) {
			if (!match && counter > sequenceSize - signal.length + 1) return -1;
			int current = iterator.next();
			if (match) {
				if (matchCounter == signal.length) return counter - matchCounter;
				if (counter != signal[matchCounter]) match = false;
				else matchCounter++;
			}
			if (!match && current == signal[0]) {
				match = true;
				matchCounter = counter;
			}
			counter++;
		}
		return -1;
	}

}

class InputReader2 {

	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader2(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public String readString() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuilder res = new StringBuilder();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}

	public boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	public String next() {
		return readString();
	}

	public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}

}


class OutputWriter2 {

	private final PrintWriter writer;

	public OutputWriter2(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}

	public OutputWriter2(Writer writer) {
		this.writer = new PrintWriter(writer);
	}

	public void print(Object... objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

	public void printLine(Object... objects) {
		print(objects);
		writer.println();
	}

	public void close() {
		writer.close();
	}

	public void flush() {
		writer.flush();
	}

}