import sys

sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))

def main():
    def dfs(aa, d=31):
        an=len(aa)
        if an == 1: return 0
        for i, a in enumerate(aa):
            if a >> d & 1: break
        else:
            i = an
        if i == 0 or i == an: return dfs(aa[:], d - 1)
        return 1 << d + min(dfs(aa[:i], d - 1), dfs(aa[i:], d - 1))

    n = II()
    aa = LI()
    aa = list(set(aa))
    aa.sort()
    print(dfs(aa))

main()