int64_t sqrt_m(int64_t x)
{
    int64_t res = sqrt(2 * x);
    if (res * (res + 1) > 2 * x)
        --res;

    return res;
}

int64_t get_sum(int64_t x)
{
    int64_t d = sqrt_m(x);
    int64_t res = d * (d + 1) * (2 * d + 1) / 6;
    int64_t delta = d * (d + 1) / 2;
    return res + (x - delta) * (d + 1);
}