import bisect

def read_data():
    N = int(input())
    As = list(map(int, input().split()))
    return N, As

def solve(N, As):
    As = list(set(As))
    As.sort()
    maxA = As[-1]
    if maxA == 0:
        return 0
    idx = 1 << (len(bin(maxA)) - 2)
    return divq(As, idx, 0, len(As))

def divq(As, idx, begin, end):
    if idx == 1 or end <= begin:
        return 0
    new_idx = idx >> 1
    if not(As[end-1] & new_idx) or As[begin] & new_idx:
        return divq(As, new_idx, begin, end)
    mid = bisect.bisect_left(As, (As[begin]&(-idx))+new_idx, begin, end)
    return new_idx + min(divq(As, new_idx, begin, mid), divq(As, new_idx, mid, end))

N, As = read_data()
print(solve(N, As))