/* STL */
#include <algorithm>
#include <deque>
#include <functional>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <utility>
#include <vector>
/* STD */
#include <iostream>
#include <string>
#include <cstdlib>
#include <math.h>
using namespace std;

void showlist (const char *str, const list<int> &L) {
	list<int>::const_iterator i;
	cout << str << endl << " ";
	for (i=L.begin(); i != L.end(); ++i)
	cout << *i << " ";
	cout << endl;
}

int main (int argc, char *argv[]) {
	list<int> L;
	int x;
	cout <<	"Enter positive integers, followed by 0:\n";
	while (cin >> x, x != 0)
		L.push_back(x);
	showlist("Initial list:", L);
	L.push_front(123);
	showlist("After inserting 123 at the beginning:", L);
	list<int>::iterator i = L.begin();
	L.insert(++i, 456);
	showlist("After inserting 456 at the second position:", L);
	i = L.end();
	L.insert(--i, 999);
	showlist("After inserting 999 just before the end:", L);
	i = L.begin(); x = *i;
	L.pop_front();
	cout << "Deleted at the beginning: " << x << endl;
	showlist("After this deletion:", L);
	i = L.end(); x = *--i;
	L.pop_back();
	cout << "Deleted at the end: " << x << endl;
	showlist("After this deletion:", L);
	i = L.begin();
	x = *++i; cout << "To be deleted: " << x << endl;
	L.erase(i);
	showlist("After this deletion (of second element):", L);
	return 0;
}