Bike loves looking for the second maximum element in the sequence. The second maximum element in the sequence of distinct numbers *x*<sub class="lower-index">1</sub>, *x*<sub class="lower-index">2</sub>, ..., *x*<sub class="lower-index">*k*</sub> (*k* &gt; 1) is such maximum element *x*<sub class="lower-index">*j*</sub>, that the following inequality holds: <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/41e9a774451aa769280692592b29103e0a6ecf97.png" style="max-width: 100.0%;max-height: 100.0%;"/>.

The lucky number of the sequence of distinct positive integers *x*<sub class="lower-index">1</sub>, *x*<sub class="lower-index">2</sub>, ..., *x*<sub class="lower-index">*k*</sub> (*k* &gt; 1) is the number that is equal to the bitwise excluding OR of the maximum element of the sequence and the second maximum element of the sequence.

You've got a sequence of distinct positive integers *s*<sub class="lower-index">1</sub>, *s*<sub class="lower-index">2</sub>, ..., *s*<sub class="lower-index">*n*</sub> (*n* &gt; 1). Let's denote sequence *s*<sub class="lower-index">*l*</sub>, *s*<sub class="lower-index">*l* + 1</sub>, ..., *s*<sub class="lower-index">*r*</sub> as *s*[*l*..*r*] (1 ≤ *l* &lt; *r* ≤ *n*). Your task is to find the maximum number among all lucky numbers of sequences *s*[*l*..*r*].

Note that as all numbers in sequence *s* are distinct, all the given definitions make sence.
The first line contains integer *n* (1 &lt; *n* ≤ 10<sup class="upper-index">5</sup>). The second line contains *n* distinct integers *s*<sub class="lower-index">1</sub>, *s*<sub class="lower-index">2</sub>, ..., *s*<sub class="lower-index">*n*</sub> (1 ≤ *s*<sub class="lower-index">*i*</sub> ≤ 10<sup class="upper-index">9</sup>).
def fun(numbers):
    
    le = len(numbers)
    li=[]
    i=0
    # le[0]=numbers[0]
    # for i in range(1,le):
    #     li[i]=numbers[i]^li[i-1]
    while i < le:
        for j in range(i+1,le):
            li.append(numbers[i]^numbers[j])
        i+=1
    return max(li)


# var1, var2,var3 = [int(x) for x in input().split()]
n = input()
user_input = input().split(' ')
numbers = [int(x.strip()) for x in user_input] 
# st = input()
# print(fun(st))

print(fun(numbers))





# # st = input()
# var1, var2 = [int(x) for x in input().split()]

# # # fun(st,var1,var2)

# # # var2 = input()
# print(fun(var1,var2))

# ############################################################3###############################

# # user_input = input().split(' ')
# # numbers = [int(x.strip()) for x in user_input] 
# # print(fun(numbers))
# ######################################################################################

#
#  def fun(m,t,r,ghost_time):
#     last_ghost = ghost_time[len(ghost_time)-1]
#     arr=[0]* last_ghost
#     x=0
#     i=0
#     candles=0
#     g_arr=[0]*last_ghost
    
#     for i in range(last_ghost):
#         if i == ghost_time[x]-1:
#             g_arr[i]=i
#             x+=1
#     x=0
   
#     while i < last_ghost and x<m:
#         if i == ghost_time[x]-1:
#             j=0
#             y=i-1
#             while j < r:
#                 arr[y]=y+t
#                 y-=1
#                 j+=1
#             i+=1
#             x+=1
#             continue    
#         i+=1
#     i=0
#     x=0
#     start=0
#     while i  < last_ghost:

#         if i!=0 and i == g_arr[i]:
#             y = i-r 
#             candles+=r
#             start = y+t
#             i
#             if start <i:
#                 return -1
#             i=start
#             continue
#         i+=1

#     return candles


# def fun1(st):
    # le = len(st)
    # stack = [0]*le
    # i=0
    # x=0
    # sh = 0
    # h=0
    # ans=list(st)
    # while i < len(ans):
    #     if ans[i]=='#' :
    #         stack[i]=stack[i-1]
    #         i+=1
    #         continue
    #     if i > 0 and ans[i] == ans[i-1]:
    #         stack[i]=(stack[i-1]+1)
    #     else:   
    #         stack[i] =0

    #     if  i < len(ans)-1 and (ans[i] != ans[i+1]) or i == len(ans)-1:
    #         p=0

    #         if i < le   and stack[i]==0:
    #             ans[i]=ans[i]
    #         elif i > 2 and stack[i] == 1 and  stack[i-2] == 1:
    #             ans[i]='#'
    #             h=1
    #             sh=0
    #             i-=2
    #         elif stack[i] != 1:
    #             h=i
    #             x=i
    #             while stack[x-1]!=0:
    #                 ans[x]='#'
    #                 x-=1
                    
    #             i = x-3
        
    #     i+=1

    # return ''.join(c  for c in ans if c!='#')