N = gets.to_i
a = gets.split.map(&:to_i)
A = a.sort + [Float::INFINITY]
def f(i, j, k, z)
  l = A.bsearch_index {|e| e >= z + 2**k}
  if k == -1
    0
  elsif l == i
    f(i, j, k - 1, z + 2**k)
  elsif l == j
    f(i, j, k - 1, z)
  else
    [f(i, l, k - 1, z), f(l, j, k - 1, z + 2**k)].min + 2**k
  end
end
ans = f(0, N, 31, 0)
puts ans