program ural01(input,output);
  var
    x,y,t:longint;
    s:comp;
  begin
    readln(x,y);
    if (x<2) or (y<2) then begin writeln(0);halt;end;
    if x>y then begin t:=x;x:=y;y:=t;end;
    if (x mod 2)=0 then s:=(x-1)*2 else s:=(x div 2)*4;
    writeln(s:0:0);
  end.