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

int main()
{
	list<int> li;        //born empty

	li.push_back(30);    //Class vector has the same push_back function,
	li.push_front(10);   //but not a push_front function.

	list<int>::iterator it = li.begin();   //it refers to the 10.
	++it;                                  //Now it refers to the 30.
	li.insert(it, 20);                     //Insert a 20 before the 30.

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

	return EXIT_SUCCESS;
}