import sys

sys.setrecursionlimit(10**8)

N = int(input())
A = list(map(int, input().split()))


def dfs(data):
    m = 0
    for a in data:
        m = max(m, a.bit_length())
    if m == 0:
        return 0
    
    large = []
    small = []
    for a in data:
        b = a.bit_length()
        if b == m:
            large.append(a ^ (1 << (m-1)))
        else:
            small.append(a)
    
    res = dfs(large)
    if small:
        res = min(res, dfs(small))
        res += 1 << (m-1)
    return res


print(dfs(A))