import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

N = int(input())
A = list(map(int, input().split()))
ans = 10**10


def rec(X, val, d):
    if d < 0:
        global ans
        ans = min(ans, val)
        return

    zero = []
    one = []
    for a in X:
        if (a >> d) & 1:
            one.append(a)
        else:
            zero.append(a)
    if one and zero:
        val += 1 << d
        rec(one, val, d - 1)
        rec(zero, val, d - 1)
    elif zero:
        rec(zero, val, d - 1)
    elif one:
        rec(one, val, d - 1)


rec(A, 0, 32)
print(ans)