program bs(input,output);

var
  i,len,counto,countx,maxo,maxx,tmp,kkk:longint;

function min(a,b:longint):longint;
  begin
    if a>b then
      exit(b)
    else
      exit(a);
  end;

begin
  assign(input,'bs.in');
  reset(input);
  assign(output,'bs.out');
  rewrite(output);

  while not(eof) do
  begin
    readln(counto,countx,maxo,maxx);

    kkk:=min(counto,countx);
    len:=kkk*2;

    countx:=countx-kkk;
    for i:=1 to kkk do
    begin
      tmp:=min(countx,maxx-1);
      dec(countx,tmp);
      len:=len+tmp;

      if tmp+1>maxx then
      begin
        kkk:=0;
        len:=0;
        countx:=0;
        break;
      end;
    end;

    counto:=counto-kkk;
    for i:=1 to kkk do
    begin
      tmp:=min(counto,maxo-1);
      dec(counto,tmp);
      len:=len+tmp;

      if tmp+1>maxo then
      begin
        counto:=0;
        break;
      end;
    end;

    if countx>0 then
      len:=len+min(countx,maxx);
    if counto>0 then
      len:=len+min(counto,maxo);

    writeln(len);
  end;

  close(input);
  close(output);
end.