import sys
sys.setrecursionlimit(10**7)
def main1(n,a):
  def func(ary):
    # aryに対する答え
    mx=max(ary)
    if mx==0:return 0
    if len(ary)==1:return 0
    bit=1<<(mx.bit_length()-1)
    nary0=[]
    nary1=[]
    for x in ary:
      if x&bit:
        nary0.append(x^bit)
      else:
        nary1.append(x)
    ret=10**10
    for nary in [nary0,nary1]:
      if not nary:continue
      elif len(nary)==len(ary):
        ret=min(ret,func(nary))
      else:
        ret=min(ret,func(nary)+bit)
    return ret
  x=func(a)
  return x

if __name__=='__main__':
  n=int(input())
  a=list(map(int,input().split()))
  ret1=main1(n,a)
  print(ret1)