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

#define pf printf
#define sf scanf

long long n,k,a,b,x,ans;

int main() {
   sf("%lld%lld%lld%lld",&n,&k,&a,&b);
   if(n == k) {
      pf("%lld",min((n-1)*a,b));
      return 0;
   }
   if(b > (n-1)*a || k == 1) {
      pf("%lld",(n-1)*a);
      return 0;
   }
   x = n;
   while(x != 1) {
      if(x % k != 0) {
         x--;
         ans += a;
      }
      else if((x-1)*a > b) {
         x /= k;
         ans += b;
      }
      else {
         ans += (x-1)*a;
         break;
      }
   }
   pf("%lld",ans);
}