program reteta;
var a,v,val:array[0..20] of integer;
    x,y,i,j,n,m:integer;
    s:longint;
    t:int64;
    suma,nr_final:real;
    f,g:text;

procedure calc(nr:integer);
  var i,j:integer;
  max:real;
  begin
  suma:=0;
  for i:=0 to m do
      if (nr and (1 shl i)<>0) then
         begin
         max:=0;
         for j:=0 to n do
             if (a[i] and  (1 shl j)<>0) then
                max:=max+v[j];
         max:=max/val[i];
         suma:=suma+max;
         end;
  end;

begin
assign(f,'reteta.in');
assign(g,'reteta.out');
reset(f);
rewrite(g);
read(f,n,m);
for i:=0 to m-1 do
    begin
    read(f,val[i]);
    read(f,x);
    a[i]:=0;
    for j:=1 to x do
        begin
        read(f,y);
        a[i]:=a[i]+1 shl (y-1);
        end;
    end;
for i:=0 to n-1 do
    read(f,v[i]);
nr_final:=20000;
for i:=1 to (1 shl m) do
    begin
    s:=0;
    for j:=0 to m-1 do
        if i and (1 shl j)<>0 then
                s:=s xor a[j];
    if (s=1 shl n -1) then
        begin
        calc(i);
        if suma<nr_final then nr_final:=suma;
        end;
    end;
t:=trunc(suma);
if t mod 10=5 then writeln(g,t div 10,'.5')
                else writeln(g,t div 10,'.0');
close(f);
close(g);
end.