#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 223450
#else
#define SIZE 223450
#endif

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

std::ostream &operator<<(std::ostream &dest, __int128_t value) {
  std::ostream::sentry s(dest);
  if (s) {
    __uint128_t tmp = value < 0 ? -value : value;
    char buffer[128];
    char *d = std::end(buffer);
    do {
      --d;
      *d = "0123456789"[tmp % 10];
      tmp /= 10;
    } while (tmp != 0);
    if (value < 0) {
      --d;
      *d = '-';
    }
    int len = std::end(buffer) - d;
    if (dest.rdbuf()->sputn(d, len) != len) {
      dest.setstate(std::ios_base::badbit);
    }
  }
  return dest;
}

__int128 parse(string &s) {
  __int128 ret = 0;
  for (int i = 0; i < s.length(); i++)
    if ('0' <= s[i] && s[i] <= '9')
      ret = 10 * ret + s[i] - '0';
  return ret;
}

__int128 calc(__int128 r) {
    __int128 base = r * K + 1;
    __int128 cnt = 0;
    REP(i,N) {
        int remain = A[i]-base;
        if (remain <= 0) continue;
        cnt += (remain+K-1)/K;
    }
    __int128 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) {
        debug("%lld, %lld\n",l,r);
        int ll = (l+l+r)/3;
        int rr = (l+r+r)/3;
        if (calc(ll) <= calc(rr)) r = rr;
        else l = ll;
    }
    __int128 ans = 2e18;
    debug("%lld ~ %lld\n", l,r);
    FOR(n,l,r+1) {
        debug("--");
        chmin(ans, calc(n));
    }
    cout << ans << endl;
}