#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define REP1(i, n) for(int i=1; i<=(n); i++)
#define RREP1(i, n) for(int i=(n); i>=1; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define out(...) printf(__VA_ARGS__)
#define chmax(a,b) a = max(a,b)
#define chmin(a,b) a = min(a,b)
#if DEBUG
#define debug(...) //printf(__VA_ARGS__)
#else
#define debug(...) /* ... */
#endif

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/
#if DEBUG
#define SIZE 100
#else
#define SIZE 123450
#endif

int N,K,X,Y,A[SIZE];

int calc(int r) {
    int base = r * K + 1;
    int cnt = 0;
    REP(i,N) {
        int remain = A[i]-base;
        if (remain <= 0) continue;
        cnt += (remain+K-1)/K;
    }
    int ret = r*Y+cnt*X;
    debug("X(%lld) * %lld + Y(%lld) * %lld = %lld\n", X,cnt, Y,r, ret);
    return ret;
}

void solve() {
    cin>>N>>K>>X>>Y;
    REP(i,N)cin>>A[i];
    int l = 0, r = 1e9;
    REP(i,100) {
        int ll = (l+l+r)/3;
        int rr = (l+r+r)/3;
        if (calc(ll) < calc(rr)) r = rr;
        else l = ll;
    }
    int ans = 1e9;
    debug("%lld ~ %lld\n", l,r);
    FOR(n,l,r+1) {
        debug("--");
        chmin(ans, calc(n));
    }
    cout << ans << endl;
}