#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
#include <iomanip>
#include <string>
using namespace std;

using ll = long long;

int main() {
	ios::sync_with_stdio(false);cin.tie(0);
	int n;
	ll k, x, y;
	cin >> n >> k >> x >> y;
	vector<ll> a(n);
	vector<ll> na(n,1);

	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}

	ll mp = 0;
	int sortcnt = 0;
	while (1) {
		int en = 0;
		for (int i = 0; i < a.size(); i++) {
			if (a[i] <= na[i]) {
				en++;
			}
		}
		if (en >= a.size()) { break; }

		int choi = 0;
		int ykk = 0;
		vector<ll> noa(n);
		for (int i = 0; i < na.size(); i++) {
			if (a[i] > na[i]) {
				ykk++;
				noa[i] = a[i] - na[i];
			}
		}

		if (y < ykk * x)choi = 1;

		if (choi == 1) {
			sort(noa.begin(), noa.end());
			if(noa[sortcnt] == 0)sortcnt++;
			ll kk = (noa[sortcnt] / k);
			if (kk == 0)kk++;
			for (int i = 0; i < na.size(); i++) {
				na[i] += k * kk;
			}mp += y * kk;
		}
		else if(choi == 0) {
			for (int i = 0; i < na.size(); i++) {
				if(a[i] > na[i]){
					ll kkk = (noa[i] / k);
					if (kkk == 0)kkk++;
					na[i] += k * kkk;
					mp += x * kkk;
					break;
				}
			}
		}
	}

	cout << mp << endl;

	return 0;
}