#coding: utf-8
##yuki_130


n=int(raw_input())
a=map(int,raw_input().split())
#print a
res=[]

for i in xrange(max(a)+1):
 s=a[:]
 for j in xrange(len(s)):
  s[j]=s[j]^i
# print i,s,max(s)
 res.append(max(s))
# print res
print min(res)