A, B, C, D, E = gets.split.map(&:to_i)

cost = 0
x = D
(1 .. A * (B - C)).each do |i|
    x = 
    if i == 1
        D
    elsif i % 10 != 0 or x < E
        x
    else
        x - E
    end
    cost += x
end

puts cost