def solve
  nums = gets.chomp.split.map(&:to_i)
  if nums[1] <= nums[2] # 参加者がいない場合
    puts 0
  else
    price_by_person = calc_by_person(nums)
    total_price = price_by_person * (nums[1] - nums[2])
    puts total_price
  end
end

def calc_by_person(nums)
  d_price = nums[3]
  return d_price if nums[0] <= 1

  prices_of_drops = [d_price]
  # 渡す個数に応じて計算
  (2..nums[0]).each do |i|
    x = prices_of_drops.last
    if (i % 10).zero?
      e = nums[4] # E price
      if e <= x
        prices_of_drops << [x - e, 0].max
      else
        prices_of_drops << x
      end
    else
      prices_of_drops << x
    end
  end

  prices_of_drops.sum
end

solve