local bls, brs = bit.lshift, bit.rshift
local mfl = math.floor
local mmi, mma = math.min, math.max
local function comp(a, b)
  return a < b
end

local function lower_bound(ary, min, max, x)
  if not comp(ary[min], x) then return min end
  if comp(ary[max], x) then return max + 1 end
  while 1 < max - min do
    local mid = mfl((min + max) / 2)
    if comp(ary[mid], x) then
      min = mid
    else
      max = mid
    end
  end
  return max
end

local n = io.read("*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n")
end
table.sort(a)
local ret = 1000000007
local function rec(l, r, stage, score, mask)
  for i = stage, 0, -1 do
    local lb = lower_bound(a, l, r, mask + bls(1, i))
    if lb <= l then
      mask = mask + bls(1, i)
    elseif r < lb then
    else
      rec(l, lb - 1, i - 1, score + bls(1, i), mask)
      rec(lb, r, i - 1, score + bls(1, i), mask + bls(1, i))
      return
    end
  end
  ret = mmi(ret, score)
end
rec(1, n, 29, 0, 0)
print(ret)