def solve(nums)
  return 0 if nums[1] <= nums[2] # 参加者がいない場合

  prices = [nums[3]]
  drop_num = (nums[1] - nums[2]) * nums[0] # 参加者 x 1人あたりの個数
  (2..drop_num).each do |i|
    x = prices.last
    if (i % 10).zero?
      e = nums[4] # E price
      if e <= x
        prices << [x - e, 0].max
      else
        prices << x
      end
    else
      prices << x
    end
  end

  prices.sum
end

nums = gets.chomp.split.map(&:to_i)
puts solve(nums)