main(n){int t,l,b,a,i,j,I,J,s;while(scanf("%d%d%d%d",&n,&t,&l,&b),n){double d[101][101]={{}},o=0;int f[101]={};while(l--)scanf("%d",&a),f[a]=1;while(b--)scanf("%d",&a),f[a]=2;d[0][0]=1;for(i=0;i<=t;i++){o+=d[i][n];d[i][n]=0;for(j=0;j<=n;j++){I=i+(f[j]==1?2:1);if(I>t)continue;for(s=1;s<7;s++){J=j+s;if(J>n)J=n-(J-n);if(f[J]==2)J=0;d[I][J]+=d[i][j]/6;}}}printf("%.9lf\n",o);}}