def calc(a, b)
  return a[0] if b < 0

  mask = 2 ** b
  p0, p1 = a.partition{|n| n & mask == 0}
  if p0.empty? then
    return calc(p1.map{|n| n ^ mask}, b - 1)
  elsif p1.empty? then
    return calc(p0, b - 1)
  else
    v1 = calc(p0.map{|n| n ^ mask}, b - 1)
    v2 = calc(p1, b - 1)
    return [v1, v2].min
  end
end

gets
a = gets.split.map(&:to_i).uniq
puts calc(a, 30)