t,l,b,a,I,J,s;main(n){while(scanf("%d%d%d%d",&n,&t,&l,&b),n){float d[101][101]={{}},o=0;int f[101]={};while(b+l--)scanf("%d",&a),f[a]=l>=0?1:2;d[0][0]=1;for(l=0;l<=t;l++){o+=d[l][n];d[l][n]=0;for(b=0;b<=n;b++){I=l+(f[b]-1?1:2);if(I<=t)for(s=1;s<7;s++){J=b+s;if(J>n)J=2*n-J;J=f[J]-2?J:0;d[I][J]+=d[l][b]/6;}}}printf("%f\n",o);}}