using System;
using System.Linq;
using CompLib.Util;

public class Program
{

    public void Solve()
    {
        var sc = new Scanner();
        int n = sc.NextInt();
        int k = sc.NextInt();
        long x = sc.NextInt();
        long y = sc.NextInt();

        int[] a = sc.IntArray();

        long[] h = new long[n];
        for (int i = 0; i < n; i++)
        {
            h[i] = (a[i] - 2 + k) / k;
        }

        // t <= n

        // xを t回する方が y1回の方が少ない
        // x*t <= y

        // 

        Array.Sort(h, (l, r) => r.CompareTo(l));

        long maxT = y / x;

        if (maxT >= n)
        {
            Console.WriteLine(h.Sum());
            return;
        }

        long ans = 0;

        long t = 0;

        for (int i = 0; i < maxT; i++)
        {
            t += h[i];
        }

        ans = y * h[maxT] + x * (t - (h[maxT] * maxT));

        Console.WriteLine(ans);
    }

    public static void Main(string[] args) => new Program().Solve();
}

namespace CompLib.Util
{
    using System;
    using System.Linq;

    class Scanner
    {
        private string[] _line;
        private int _index;
        private const char Separator = ' ';

        public Scanner()
        {
            _line = new string[0];
            _index = 0;
        }

        public string Next()
        {
            while (_index >= _line.Length)
            {
                _line = Console.ReadLine().Split(Separator);
                _index = 0;
            }

            return _line[_index++];
        }

        public int NextInt() => int.Parse(Next());
        public long NextLong() => long.Parse(Next());
        public double NextDouble() => double.Parse(Next());
        public decimal NextDecimal() => decimal.Parse(Next());
        public char NextChar() => Next()[0];
        public char[] NextCharArray() => Next().ToCharArray();

        public string[] Array()
        {
            _line = Console.ReadLine().Split(Separator);
            _index = _line.Length;
            return _line;
        }

        public int[] IntArray() => Array().Select(int.Parse).ToArray();
        public long[] LongArray() => Array().Select(long.Parse).ToArray();
        public double[] DoubleArray() => Array().Select(double.Parse).ToArray();
        public decimal[] DecimalArray() => Array().Select(decimal.Parse).ToArray();
    }
}