#include <bits/stdc++.h>
using namespace std;
int main()
{ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
long long n,k,a,b,x,c=0;
cin >>n;
cin >>k;
cin >>a;
cin >>b;
   if(b > (n-1)*a || k == 1)
    {
    cout <<((n-1)*a);
      return 0;
   }
   x = n;
   while(x != 1) {
      if(k >= x && (x-1)*a <= b) {
         c += (x-1)*a;
         break;
      }
      else if(x % k == 0 && (x-1)*a >= b) {
         c += b;
         x /= k;
      }
      else{
         c += a*(x%k);
         x -= (x%k);
      }
   }
  cout <<c;
}