#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

int main() {
    ll n, k, x, y;
    cin >> n >> k >> x >> y;
    vector<int> v(n);
    for (auto &&i : v) scanf("%d", &i);
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        a[i] = (v[i]-1+k-1)/k;
    }
    a.emplace_back(0);
    sort(a.begin(),a.end());
    ll ans = INF<ll>, val = 0;
    for (int i = 0; i <= n; ++i) {
        val += a[i];
    }
    for (int i = 0; i <= n; ++i) {
        val -= a[i];
        while(i+1 <= n && a[i+1] == a[i]) val -= a[++i];
        ans = min(ans, (val-(ll)(n-i)*a[i])*x+y*a[i]);
    }
    cout << ans << "\n";
    return 0;
}