#include <algorithm>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define rep(i, n) for(int(i) = 0; (i) < (n); (i)++)
#define FOR(i, m, n) for(int(i) = (m); (i) < (n); (i)++)
#define All(v) (v).begin(), (v).end()
#define pb push_back
#define MP(a, b) make_pair((a), (b))
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int INF = 1 << 30;
const ll LINF = 1LL << 60;
const int MOD = 1e9 + 7;

int main() {
    ll N;
    ll K, X, Y;
    cin >> N >> K >> X >> Y;
    vector<ll> A(N);
    rep(i, N) cin >> A[i];
    rep(i, N) A[i] -= 1;
    sort(All(A));
    vector<ll> B(N);
    rep(i, N) { B[i] = A[i] / K + !!(A[i] % K); }
    int c = 0;
    while(c < N && (N - c) * X > Y)
        c++;
    ll rest = 0;
    FOR(i, c, N) {
        if(c > 0)
            rest += B[i] - B[c - 1];
        else
            rest += B[i];
    }
    ll res = rest * X;
    if(c != 0)
        res += B[c - 1] * Y;
    cout << res << endl;
    return 0;
}