local mmi, mma = math.min, math.max
local mfl, mce = math.floor, math.ceil
local n, k = io.read("*n", "*n")
local x, y = io.read("*n", "*n")
local t = {}
for i = 1, n do
  local a = io.read("*n")
  t[i] = mce((a - 1) / k)
end
table.sort(t)
local lim = mce(y / x)
lim = mmi(lim, n + 1)
k = 0LL + k
x, y = 0LL + x, 0LL + y
local ret = 0LL
local cursum = 0LL
for i = 1, n do
  t[i] = 0LL + t[i]
end
for i = 1, n + 1 - lim do
  if cursum < t[i] then
    local rem = t[i] - cursum
    ret = ret + rem * y
    cursum = cursum + rem
  end
end
for i = n + 2 - lim, n do
  local rem = t[i] - cursum
  if 0 < rem then
    ret = ret + rem * x
  end
end
local str = tostring(ret):gsub("LL", "")
print(str)