Sets are a part of the C++ STL. Sets are containers that store unique elements following a specific order. Here are some of the frequently used member functions of sets:

• Declaration:

  set<int>s; //Creates a set of integers.
  

• Size:

  int length=s.size(); //Gives the size of the set.
  

• Insert:

  s.insert(x); //Inserts an integer x into the set s.
  

• Erasing an element:

  s.erase(val); //Erases an integer val from the set s.
  

• Finding an element:

  set<int>::iterator itr=s.find(val); //Gives the iterator to the element val if it is found otherwise returns s.end() .
  Ex: set<int>::iterator itr=s.find(100); //If 100 is not present then it==s.end().
  

  To know more about sets click Here. Coming to the problem, you will be given queries. Each query is of one of the following three types:
  
  : Add an element to the set.
  : Delete an element from the set. (If the number is not present in the set, then do nothing).
  : If the number is present in the set, then print "Yes"(without quotes) else print "No"(without quotes).