#include <iostream>
#include <string>
#include <stack>
#include <list>
#include <forward_list>
using namespace std;

void EraseAtPos(int Pos, list<int>& L)
{
    list<int>::iterator It = L.begin();
    int i = 0;
    while (i < Pos)
    {
        It++;
        i++;
    }
    L.erase(It);

}
void DoOperations(list<list<int>>& L){
    int pos = 0;
    bool isEven = false;
    int i = 0;
    list<list<int>>::iterator It;
    for (It = L.begin(); It != L.end(); ++It)
    {
        if (L.size() % 2 == 0)
        {
            if (isEven)
            {
                i = 1;
                isEven = false;
            }
            else
            {
                i = 0;
                isEven = true;
            }
        }
        else
        {
            i = 0;
        }
        pos = i;
        while (i < It->size())
        {
            EraseAtPos(pos, *It);
            pos++;
            i++;
        }
    }
}
int main()
{

    list<list<int>> GList;
    //GList.resize(10);

    list<int> l1;
    //l1.resize(10);
    l1.push_back(1);
    l1.push_back(2);
    l1.push_back(3);
    l1.push_back(4);
    //l1.push_back(20);

    list<int> l2;
    //l2.resize(10);
    l2.push_back(5);
    l2.push_back(6);
    l2.push_back(7);
    l2.push_back(8);
    //l2.push_back(21);

    list<int> l3;
    //l3.resize(10);
    l3.push_back(9);
    l3.push_back(10);
    l3.push_back(11);
    l3.push_back(12);
    //l3.push_back(22);

    list<int> l4;
    //l4.resize(10);
    l4.push_back(13);
    l4.push_back(14);
    l4.push_back(15);
    l4.push_back(16);
    //l4.push_back(22);

    list<int> l5;
    //l5.push_back(30);
    //l5.push_back(40);
    //l5.push_back(50);
    //l5.push_back(60);
    //l5.push_back(70);



    GList.push_back(l1);
    GList.push_back(l2);
    GList.push_back(l3);
    GList.push_back(l4);
    //GList.push_back(l5);

    list<list<int>>::iterator Iter;
    for (Iter = GList.begin(); Iter != GList.end(); ++Iter)
    {
        list<int> sublist = *(Iter);
        list<int>::iterator SubIt;
        for (SubIt = sublist.begin(); SubIt != sublist.end(); ++SubIt)
        {
            cout << *(SubIt) << " ";
        }
        cout << endl;
    }


    DoOperations(GList);
    for (Iter = GList.begin(); Iter != GList.end(); ++Iter)
    {
        list<int> sublist = *(Iter);
        list<int>::iterator SubIt;
        for (SubIt = sublist.begin(); SubIt != sublist.end(); ++SubIt)
        {
            cout << *(SubIt) << " ";
        }
        cout << endl;
    }
}