eval"N,M,*A="+gets(p).split*?,
r = A.pop(M)
curr = r.inject:^
loop{
  i=rand(M)
  j=rand(N-M)
  r[i], A[j] = A[j], r[i]
  curr ^= A[j] ^ r[i]
  if curr == (1<<20)-1
    puts A*" "
    exit
  end
}