#include <iostream>
#include <cstdlib>
#include <list>
using namespace std;

int main()
{
	const int a[] = {30, 20, 30, 10, 20, 10};
	const size_t n = sizeof a / sizeof a[0];
	list<int> li(a, a + n);

	for (list<int>::const_iterator it = li.begin(); it != li.end(); ++it) {
		cout << *it << "\n";
	}
	cout << "\n";

	for (list<int>::iterator it = li.begin(); it != li.end();) {
		if (*it == 20) {
			it = li.erase(it);           //Get rid of one 20.
		} else {
			++it;
		}
	}

	li.remove(30);                       //Get rid of every 30.

	for (list<int>::const_iterator it = li.begin(); it != li.end(); ++it) {
		cout << *it << "\n";
	}
	cout << "\n";

	cout << "size == " << li.size() << "\n";
	li.clear();
	cout << "size == " << li.size() << "\n";
	return EXIT_SUCCESS;
}