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

def calc(now,l,b):
    if b == -1:
        return now
    one = []
    zero = []
    mask = 1 << b
    for i in l:
        if i & mask:
            one.append(i)
        else:
            zero.append(i)
    if len(one) == 0 or len(zero) == 0:
        return calc(now,l,b-1)
    else:
        t1 = calc(now | mask,one,b-1)
        t2 = calc(now | mask,zero,b - 1)
        return min(t1,t2)
print(calc(0,a,30))