long long m, d, mid, high, low=0, mini=1000000000;

int check(long long num)
{

    long long divi = 1, day=1, sum=0;

    while (num/divi > 0)
    {
        if (sum > m) return 0;
        else if (sum == m) return 1;

        if (day == 1) sum += num;
        else if (day == 2) sum += num/day;
        else
        {
            divi *= d*(d+day-2);
            sum += num/divi;
        }
        day++;
    }

    return 2;
}

int main()
{
    cin >> m >> d;
    high = m;

    while (low < high)
    {
        mid = (high + low) / 2;

        if (check(mid) == 1)
        {
            mini = mid;
            break;
        }
        else if (check(mid) == 0)
        {
            if (mid < mini) mini = mid;
            high = mid;
        }

        else low = mid;

    }

    cout << mini;


}