class Calc0027
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @vs = args.shift.map(&:to_i)
  end

  def run
    min = nil
    (1..30).each do |a|
      (a..30).each do |b|
        (b..30).each do |c|
          r = calc_min([a, b, c])
          min = r if !min || r && min > r
        end
      end
    end
    min
  end

  def calc_min(bs)
    memo = Array.new(31)
    memo[0] = 0

    bs.each do |b|
      (1..30).each do |m|
        if m >= b 
          r = [memo[m], (memo[m - b] ? memo[m - b] + 1 : nil)].compact
          memo[m] = r.min unless r.empty?
        end
      end
    end

    r = @vs.map { |v| memo[v] }
    if r.all?
      r.inject(:+)
    else
      nil
    end
  end
end

puts Calc0027.new(STDIN.readlines).run if __FILE__ == $0