The illustration shows a code segment with the lines numbered from 1 through 31 and the annotations are as follows:

"//Program to demonstrate use of the set template class.
 #include <iostream>
 #include <set>
 using std::cout;
using std::endl;
 using std::set;
 int main()
 {
 set<char> s;
s.insert('A');”
 “s.insert('D');
 s.insert('D');
 s.insert('C');
 s.insert('C');” annotated as "No matter how many times you add an element to a set, the set contains only one copy of that element."
 “s.insert('B');
 cout << "The set contains:\n";
 set<char>::const_iterator p;
 for (p = s.begin(); p != s.end(); p++)
 cout << *p << " ";
 cout << endl;
 cout << "Removing C.\n";
 s.erase('C');
 for (p = s.begin(); p != s.end(); p++)
 cout << *p << " ";
 cout << endl;

 return 0;
 }"