def dfs(d, a):
    if len(a) == 1:
        return 0

    a0 = []
    a1 = []
    b = 1 << d
    for n in a:
        if n & b:
            a1.append(n)
        else:
            a0.append(n)

    if not a0 or not a1:
        if d == 0:
            return 0
        return dfs(d - 1, a)
    else:
        if d == 0:
            return 1
        return b + min(dfs(d - 1, a0), dfs(d - 1, a1))


def solve(N, A):
    return dfs(30, A)


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

    print(solve(N, A))


if __name__ == '__main__':
    main()