第一行包含整数 n 和 m（1≤n，m≤105） - 团队参与者的数量和消息的数量。接下来的 m 行中的每一行都包含以下格式的消息：
'+ id'：记录表示号码 ID为 （1≤id≤n） 的人员已登录到会议。
'- id'：记录表示号码为ID （1≤id≤n） 的人员已从会议注销。
假设团队中的所有人员都从 1 到 n 编号，消息按时间顺序给出。保证给定的顺序是会议连续部分的正确记录。保证不会同时发生两个登录/注销事件。
输出
在第一行打印整数 k （0≤k≤n） − 有多少人可以成为领导者。在下一行中，按递增顺序打印 k 个整数 - 可以成为领导者的人数。
如果数据使得团队中没有成员可以成为领导者，请打印单个数字 0。
例子
输入
5 4
+ 1
+ 2
- 2
- 1
输出
4
1 3 4 5
输入
3 2
+ 1
- 2
输出
1
3
输入
2 4
+ 1
- 1
+ 2
- 2
输出
0
输入
5 6
+ 1
- 1
- 3
+ 3
+ 4
- 4
输出
3
2 3 5
输入
2 4
+ 1
- 2
+ 2
- 1
输出
0
B. Online Meeting
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Nearly each project of the F company has a whole team of developers working on it. They often are in different rooms of the office in different cities and even countries. To keep in touch and track the results of the project, the F company conducts shared online meetings in a Spyke chat.
One day the director of the F company got hold of the records of a part of an online meeting of one successful team. The director watched the record and wanted to talk to the team leader. But how can he tell who the leader is? The director logically supposed that the leader is the person who is present at any conversation during a chat meeting. In other words, if at some moment of time at least one person is present on the meeting, then the leader is present on the meeting.
You are the assistant director. Given the 'user logged on'/'user logged off' messages of the meeting in the chronological order, help the director determine who can be the leader. Note that the director has the record of only a continuous part of the meeting (probably, it's not the whole meeting).
Input
The first line contains integers n and m(1≤n,m≤105) − the number of team participants and the number of messages. Each of the next m lines contains a message in the format:
'+ id': the record means that the person with number id(1≤id≤n) has logged on to the meeting.
'- id': the record means that the person with number id(1≤id≤n) has logged off from the meeting.
Assume that all the people of the team are numbered from 1 to n and the messages are given in the chronological order. It is guaranteed that the given sequence is the correct record of a continuous part of the meeting. It is guaranteed that no two log on/log off events occurred simultaneously.
Output
In the first line print integer k(0≤k≤n) − how many people can be leaders. In the next line, print k integers in the increasing order − the numbers of the people who can be leaders.
If the data is such that no member of the team can be a leader, print a single number 0.