import sequtils
template `max=`*(x,y) = x = max(x,y)
template `min=`*(x,y) = x = min(x,y)

proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "<stdio.h>" .}
proc scan(): int =
  while true:
    let k = getchar_unlocked()
    if k < '0': break
    result = 10 * result + k.ord - '0'.ord

# 14C2 * 12C2 * 10C2 * 8C2 * 6C2 * 4C2 * 2C2
# 高々:1*6*15*28*45*66*91 なので全て列挙
proc solve(A:seq[int]):int =
  if A.len == 2: return A[0] xor A[1]
  for x in 0..<A.len:
    for y in (x+1)..<A.len:
      result .max= solve(A[0..<x] & A[x+1..<y] & A[y+1..^1]) + (A[x] xor A[y])

let n = scan()
let A = newSeqWith(n,scan())
echo solve(A)