#include <bits/stdc++.h>
using namespace std;
long long n, k, A, B, ans = 0;
long long fmin() {
  long long pros = (n - (n / k)) * A;
  if (B < pros) {
    n = n / k;
    return B;
  } else {
    n = n / k;
    return pros;
  }
}
int main() {
  cin >> n;
  cin >> k;
  cin >> A;
  cin >> B;
  if (k == 1) {
    cout << (n - 1) * A;
    return 0;
  }
  while (n != 1) {
    if (n >= k) {
      if (n % k == 0) {
        ans += fmin();
      } else {
        long long t = (n % k);
        n = n - t;
        ans += (A * t);
      }
    } else {
      ans = ans + (n - 1) * A;
      n = 1;
    }
  }
  cout << ans;
  return 0;
}
