class Yukicoder
  def initialize
    aw, ab = gets.chomp.split(' ').map(&:to_i)
    bw, bb = gets.chomp.split(' ').map(&:to_i)
    c, d   = gets.chomp.split(' ').map(&:to_i)

    mw1 = [aw, [0, (c - ab)].max].min

    aw -= mw1
    bw += mw1

    mw2 = [bw, d].min

    aw += mw2
    bw -= mw2

    puts aw
  end
end

Yukicoder.new