class Calc0131
  def initialize(args)
    args = args.map { |l| l.chomp.split(/\s+/) }
    @x, @y, @d = args.shift.map(&:to_i)
  end

  def run
    if @d > @x + @y
      0
    else
      c = @d + 1
      c -= (@d - @x) if @d > @x
      c -= (@d - @y) if @d > @y
      c
    end
  end
end

puts Calc0131.new(STDIN.readlines).run if __FILE__ == $0