void multiply(ull* big, ull small)
{
    ull pr = 0;
    for(int i = 0; i < 40; i++)
    {
        big[i] *= small;
        big[i] += pr;
        pr = big[i] / 10;
        big[i] %= 10;
    }
}
void add(ull* big1, ull* big2)
{
    bool pr = 0;
    for(int i = 0; i < 40; i++)
    {
        //cout << big1[i]  << " ";
        big1[i] = big1[i] + big2[i] + pr;
       // cout << big1[i]  << " ";
       // cout << "\n";
        pr = big1[i] / 10;
        big1[i] %= 10;
    }
}
void subtract(ull* big1, ull* big2)
{
    ull non_zero = 40;
    for(int i = 39; i >= 0; i--)
    {
        if(big1[i] != 0 || big2[i] != 0)
        {
            if(big1[i] >= big2[i])
                big1[i] -= big2[i];
            else
            {
                big1[non_zero]--;
                for(int j = non_zero - 1; j > i; j--)
                {
                    big1[j] = 9;
                }
                big1[i] = big1[i] + 10 - big2[i];
            }
        }
        //cout << big1[i] << " ";
        if(big1[i] != 0)
            non_zero = i;
    }
}