def solve(A, b):
    if b == -1:
        return 0
    u = [a for a in A if not(a & (1 << b))]
    d = [a ^ (1 << b) for a in A if a & (1 << b)]

    if len(u) == 0:
        return solve(d, b-1)
    if len(d) == 0:
        return solve(u, b-1)
    return min(solve(d, b-1), solve(u, b-1)) + (1 << b)


def main():
    input()  # N
    *A, = map(int, input().split())
    print(solve(A, 29))


if __name__ == '__main__':
    main()