注意導遊！

程式碼：

const
  maxn=1000000;
var
  a:array[0..maxn] of longint;
  i,x,y,ans,n,p:longint;
begin
   assign(input,'museum.in');reset(input);
  assign(output,'museum.out');rewrite(output);
  readln(n);
  p:=1;
  for i:=1 to n do
    begin
      read(x);
      if x=0 then
       begin
        readln(a[p]);
        inc(ans,a[p]+1
 
);
        inc(p);
       end
      else begin
             readln(y);
             dec(ans,a[y]+1);
           end;
    end;
  writeln(ans);
  close(input);close(output);
end.