#include <bits/stdc++.h>
using namespace std;

int main() {
  long long H, A, Ans = 0, Pow = 1; cin >> H >> A;
  for (long long i = 0; H / Pow > 0; i++) {
    Ans += ((long long)1 << i);
    Pow *= A;
  }
  cout << Ans << endl;
}