from bisect import bisect_left
max2 = lambda x,y: x if x > y else y
min2 = lambda x,y: x if x < y else y

def solve(a):
    a.sort()
    def rec(d,l,r):
        if l + 1 == r or d == 0:
            return 0
        i = a[l]&(-1 << d)|(1<<(d-1))
        m = bisect_left(a,i)
        if l == m or r == m:
            return rec(d-1,l,r)
        return min2(rec(d-1,l,m),rec(d-1,m,r))|(1<<(d-1))
    return rec(32,0,len(a))


n = int(input())
a = list(map(int,input().split()))
print(solve(a))