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