#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;
 
#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define pi M_PI
 
typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

int main() {
    int n, t, l, b;
    while (cin >> n >> t >> l >> b && n){
        VI a(n+1);
        while (l--){
            int x;
            cin >> x;
            a[x] = 1;
        }
        while (b--){
            int x;
            cin >> x;
            a[x] = 2;
        }
        vector<vector<double> > dp(t+2, vector<double>(n+1));
        dp[0][0] = 1.0;
        REP(i,t){
            REP(j,n){
                FOR(k,1,6){
                    int next = j + k;
                    if (next > n) next = 2*n - next;
                    if (a[next] == 2) next = 0;
                    if (a[next] != 1) dp[i+1][next] += 1.0/6.0 * dp[i][j];
                    else dp[i+2][next] += 1.0/6.0 * dp[i][j];
                }
            }
            dp[i+1][n] += dp[i][n];
        }
        printf("%.10f\n", dp[t][n]);
    }
    return 0;
}