import sequtils,algorithm template `max=`*(x,y) = x = max(x,y) template `min=`*(x,y) = x = min(x,y) proc getchar_unlocked():char {. importc:"getchar_unlocked",header: "" .} proc scan(): int = while true: let k = getchar_unlocked() if k < '0': break result = 10 * result + k.ord - '0'.ord let n = scan() let A = newSeqWith(n,scan()) proc solve(s:int) : int = for i in 0.. 0 : continue for j in (i+1).. 0 : continue result .max= (A[i] + A[j]) xor solve(s or (1 shl i) or (1 shl j)) # 最高のペアが分かったのでbreakしてよい break echo solve(0)