I searched the forum,and used the data you offered.It seems to be all right,but wa on test 5...
my code shown below,thx:)

{$N+}

var
   a,b:extended;
   total:longint;
   i,j:longint;
   max,now:extended;
   x,y,key1,key2:extended;
begin
  readln(a,b);
  readln(total);
  close(input);
  max:=-1;
  for i:=0 to total do
   begin
     x:=round((a-b+2*i)/4);
     y:=i-x;
     now:=a*x+b*y-x*x-y*y;
     if now>max then
     begin
       max:=now;
       key1:=x;
       key2:=y;
     end
     else if now=max then
      if y<key2 then
      begin
       key1:=x;
       key2:=y;
      end;
   end;
   writeln(max:0:2);
   write(KEY1:0:0,' ',KEY2:0:0);
end.