eval"N,M,*A="+gets(p).split*?,
curr = A[0...M].inject:^
loop.any?{
  i = rand M
  j = rand N-M
  A[i], A[j] = A[j], A[i]
  curr ^= A[i] ^ A[j]
  curr == (1<<20)-1&&$><<A[0...M]*" "
}