pii find_pos(int pos)
{
    int bl = 0;
    for (auto x : q)
    {
        if (pos >= x.size())
            pos -= x.size(), ++bl;
        else
            return mk(bl, pos);
    }
}

void add_block_build(int pos)
{
    q.inb(a);
    if (pos)
    {
        ll x = q[pos - 1].back();
        q[pos - 1].pop_back();
        q[pos].inb(x);
    }
}

void add_block(int pos)
{
    vll sw;
    int sz = q[pos - 1].size();
    for (int i = sz - 1; i >= sz / 2; --i)
    {
        sw.inb(q[pos - 1].back());
        q[pos - 1].pop_back();
    }
    reverse(all(sw));
    q.insert(q.begin() + pos, sw);
}

void add_x(ll x)
{
    q.back().inb(x);
    ANS += x * x;
    if (q.back().size() == LEN)
        add_block_build(q.size());
}

void delete_block(int pos)
{
    q.erase(q.begin() + pos);
}