import sequtils,strutils,algorithm
var
    N = stdin.readline.parseInt
    A2 = stdin.readline.split.map(parseInt)
    flag : array[100001, bool]
A2.sort(system.cmp)
flag[0] = true
var A = newSeq[int](0)
for i,a in A2:
    if i == 0:
        A.add(a)
        continue
    if a != A2[i - 1]:
        A.add(a)
var
    p,k : int
    ans : int
block tansaku:
    for i in countdown(29, 0):
        var f : bool
        for j in 1..<A.len:
            if ((1 shl i) and A[j]) != ((1 shl i) and A[j - 1]):
                if flag[j - 1]:
                    p = j - 1
                    k = i
                    ans += (1 shl i)
                    break tansaku
                f = true
                flag[j] = true
        if f:
            ans += (1 shl i)
echo ans