class Calc0091
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @r, @g, @b = args.shift.map(&:to_i)
  end

  def run
    min, max = 0, (@r + @g + @b) / 3 + 1
    bs(min, max)
  end

  def bs(min, max)
    cur = (min + max) / 2
    if cur == min
      cur
    else
      check(cur) ? bs(cur, max) : bs(min, cur)
    end
  end

  def check(k)
    lack = [@r, @g, @b].map { |s| k - s }.select(&:positive?).inject(:+) || 0
    excess = [@r, @g, @b].map { |s| (s - k) / 2 }.select(&:positive?).inject(:+) || 0
    excess >= lack
  end
end

puts Calc0091.new(STDIN.readlines).run if __FILE__ == $0