program bs;
var countO,countX,maxO,maxX:word;
procedure swap(var m,n:word);
var t:word;
begin
  t:=m; m:=n; n:=t;
end;
function find(a,b,x,y:word):word;
begin
  if x+y=0 then exit(0);
  if x=0 then exit(b); if y=0 then exit(a);
  if a=b then exit(a+b);
  if a<b then begin swap(a,b); swap(x,y); end;
  //writeln(a,'+',b,'=',a+b,'  ',x,' ',y);
  if (b*y<a+b)and(2*b+x<a+b) then exit(2*b+x);
  if b*(x+1)+x<=a+b
    then exit(b*(x+1)+x)
    else exit(a+b);
end;
begin
  assign(input,'bs.in'); reset(input);
  assign(output,'bs.out'); rewrite(output);
  while not eof do
  begin
    readln(countO,countX,maxO,maxX);
    if countO+countX+maxO+maxX>0 then
      writeln(find(countO,countX,maxO,maxX));
  end;
  close(input); close(output);
end.