import sequtils,strutils,algorithm,math
var
    N = stdin.readline.parseInt
    A2 = stdin.readline.split.map(parseInt)
    flag : array[100001, bool]

proc solve(d : int, A : openarray[int]) : int =
    if A.len <= 1 or d == 0:
        return 0
    var
        B = newSeqWith(2, newSeq[int](0))
    for a in A:
        B[((a shr d) and 1)].add(a - (1 shl d))
    if B[0].len == 0:
        return solve(d - 1, B[1])
    elif B[1].len == 0:
        return solve(d - 1, B[0])
    else:
        return (1 shl d) + min(solve(d - 1, B[0]), solve(d - 1, B[1]))

echo solve(29, A2)