#include <bits/stdc++.h>

using namespace std;

int main()
{
    long long n, k, a, b;
    cin >> n >> k >> a >> b;
    if (k == 1)
    {
        cout << (n-1)*a;
        return 0;
    }
    long long ans = 0;
    while (n >= k)
    {
        ans += (n%k) * a;
        n -= n%k;
        while (n%k == 0 && n >= k)
        {
            long long mn = min(b, (n - n/k) * a);
            ans += mn;
            n /= k;
        }
    }
    cout << ans + (n-1)*a;
}