function

list<int>& function1(list<int>& l)
{
    int n = l.size();
    int i = 0;
    list<int>::iterator it = l.begin();
    while (it != l.end())
    {
        if (*it == n - i - 1)
        {
            it = l.erase(it);
        }
        else
        {
            ++it;
        }
        ++i;
    }
    return l;
}