import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.text.DecimalFormat;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;

public class Main {

	static PrintWriter out;
	static InputReader ir;
	static boolean debug = false;
	static double[][] dp;
	static int n, t;
	static boolean[] lose, back;

	static void solve() {
		DecimalFormat df = new DecimalFormat("0.000001");
		while (true) {
			n = ir.nextInt();
			if (n == 0)
				return;
			t = ir.nextInt();
			int l = ir.nextInt();
			int b = ir.nextInt();
			lose = new boolean[n + 1];
			back = new boolean[n + 1];
			for (int i = 0; i < l; i++)
				lose[ir.nextInt()] = true;
			for (int i = 0; i < b; i++)
				back[ir.nextInt()] = true;
			dp = new double[t + 2][n + 1];
			for (int i = 0; i <= t + 1; i++)
				Arrays.fill(dp[i], -1.0);
			out.println(df.format(dfs(0, 0)));
		}
	}

	static double dfs(int turn, int cur) {
		if (cur == n)
			return 1.0;
		if (turn >= t)
			return 0.0;
		if (dp[turn][cur] >= 0.0)
			return dp[turn][cur];
		double ret = 0.0;
		for (int i = 1; i <= 6; i++) {
			int nxt = cur + i;
			if (nxt > n)
				nxt = 2 * n - nxt;
			if (lose[nxt])
				ret += dfs(turn + 2, nxt) / 6.0;
			else if (back[nxt])
				ret += dfs(turn + 1, 0) / 6.0;
			else
				ret += dfs(turn + 1, nxt) / 6.0;
		}
		return dp[turn][cur] = ret;
	}

	public static void main(String[] args) throws Exception {
		ir = new InputReader(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.flush();
	}

	static class InputReader {

		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;

		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}

		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}

		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}

		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}

		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}

		public boolean hasNext() {
			skip();
			return hasNextByte();
		}

		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}

		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}

		public long[] nextLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}

		public char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}

	static void tr(Object... o) {
		if (debug)
			out.println(Arrays.deepToString(o));
	}
}


Measured memory_bytes: 27552