function roll(point : integer) : real;
begin
   case point of
     2,12: roll := 1/36;
     3,11: roll := 2/36;
     4,10: roll := 3/36;
     5,9: roll := 4/36;
     6,8: roll := 5/36;
     7: roll := 6/36;
   else
       writeln('invalid roll');
       roll := 0;
   end; { case }
end; { rolls }