#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;

template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }

const int INF = 1L << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（右, 下, 左, 上）
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;


int main() {
    cin.tie(0);
	ios::sync_with_stdio(false);

    while (true) {
        int N, T, L, B;
        cin >> N >> T >> L >> B;
        if ((N + T + L + B) == 0) {
            break;
        }

        vector<int> f(N + 1, 0);
        FOR(i, 0, L) {
            int l;
            cin >> l;
            f[l] = 1;
        }
        FOR(i, 0, B) {
            int b;
            cin >> b;
            f[b] = 2;
        }

        vector<vector<double>> dp(T + 10, vector<double>(N + 1, 0));
        dp[0][0] = 1.0;
        FOR(i, 0, T) {
            FOR(j, 0, N + 1) {
                if (dp[i][j] == 0) {
                    continue;
                }

                FOR(k, 1, 7) {
                    int next = j + k;
                    if (next >= N + 1) {
                        next = N - (k - (N - j));
                    }
                    if (next == N) {
                        continue;
                    }

                    if (f[next] == 0) {
                        dp[i + 1][next] += dp[i][j] * (1.0 / 6.0);
                    }
                    if (f[next] == 1) {
                        dp[i + 2][next] += dp[i][j] * (1.0 / 6.0);
                    }
                    if (f[next] == 2) {
                        dp[i + 1][0] += dp[i][j] * (1.0 / 6.0);
                    }
                }
            }
        }


        double ans = 1.0;
        FOR(i, 0, N + 1) {
            ans -= dp[T][i];
            ans -= dp[T + 1][i];
        }

        cout << fixed << setprecision(6) << ans << endl;
    }

	return 0;
}


Measured memory_bytes: 3336