我哭了，90分，第三个wa

#include <iostream>
using namespace std;
int main()
{
    int  n, k, sum = 0, num = 0;
    cin >> n >> k;
    while (n != 0) 
    {
        if (num / k >= 1) 
    { 
        num = 0;
        n=n + 1;
    }
    sum = sum + n;
    num = num + n % k;
    n = n / k;
}
cout << sum;
system("pause");
return 0;

} 28 3输出41没问题啊