#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
using ll = long long;
using u64 = uint_fast64_t;
using pii =  pair<int, int>;
using pll =  pair<long long, long long>;
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()
constexpr char ln =  '\n';
constexpr long long MOD = 1000000007;
//constexpr long long MOD = 998244353;
template<class T1, class T2> inline bool chmax(T1 &a, T2 b) { if (a < b) { a = b; return true;} return false; }
template<class T1, class T2> inline bool chmin(T1 &a, T2 b) { if (a > b) { a = b; return true;} return false; }
inline int popcount(int x) {return __builtin_popcount(x);}
inline int popcount(long long x) {return __builtin_popcountll(x);}
void print() { cout << "\n"; }
template<class T, class... Args>
void print(const T &x, const Args &... args) {
    cout << x << " ";
    print(args...);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);
    ll N,K,X,Y; cin >> N >> K >> X >> Y;
    vector<ll> A(N);
    rep(i,N) cin >> A[i];

    auto calc=[&](ll x) {
        ll ret = x*Y;
        rep(i,N) {
            ll val = A[i] - K*x;
            if (val > 1) {
                ret += (val-1+K-1)/K*X;
            }
        }
        return ret;
    };

    ll ok = 0;
    ll ng = 2e9;
    while (ng - ok > 1) {
        ll mid = (ok+ng)/2;
        if (calc(mid) - calc(mid-1) <= 0) ok = mid;
        else ng = mid;
    }

    cout << calc(ok) << ln;
}