BigInt

string Add(int toAdd)
    {
        string result = "";
        int reminder = 0;
        for (int i = number.size() - 1; i >= 0; i--)
        {
            char num = number[i];
            int n = num - '0';
            int second = toAdd % 10;
            toAdd /= 10;
            n += second + reminder;
            reminder = 0;
            if (n >= 10)
            {
                reminder = 1;
                n -= 10;
            }
            result.insert(result.begin(), (char)n + '0');
        }
        if (reminder)
        {
            result.insert(result.begin(), (char)reminder + '0');
        }
        return result;
    }


    string Subtract(int toSub)
    {
        string result = "";
        int outcome, carry = 0;
        for (int i = number.size() - 1; i >= 0; i--)
        {
            char num = number[i];
            int n = num - '0';
            int second = toSub % 10;
            toSub /= 10;
            outcome = (n - second) - carry;
            if (outcome < 0)
            {
                outcome += 10;
                carry = 1;
                result.insert(result.begin(), (char)outcome + '0');

            }
            else
            {
                carry = 0;
                result.insert(result.begin(), (char)outcome + '0');
            }
        }
        return result;
    }

    string Mulitply(int toMultiply)
    {
        string toMulti = to_string(toMultiply);
        int n = number.size();
        int m = toMulti.size();
        string res(m + n, '0');

        for (int i = n - 1; i >= 0; i--) {
            for (int j = m - 1; j >= 0; j--) {
                int p = (number[i] - '0') * (toMulti[j] - '0') + (res[i + j + 1] - '0');
                res[i + j + 1] = p % 10 + '0';
                res[i + j] += p / 10;
            }
        }
        return res;
    }

    string Division(int divisor) {
            string ans;
            int idx = 0;
            int temp = number[idx] - '0';
            while (temp < divisor)
                temp = temp * 10 + (number[++idx] - '0');

            while (number.size() > idx) {
                ans += (temp / divisor) + '0';

                temp = (temp % divisor) * 10 + number[++idx] - '0';
            }

            if (ans.length() == 0)
                return "0";
            return ans;
        }