def solution(start, length):
  guardPass = length
  checksum = 0 # doesn't affect checksum since 0 xor n = n
  while guardPass > 0: # tracks how many workers guards are checking
    for i in range(guardPass): # checks workers
      checksum = checksum ^ start
      start += 1
    start += length - guardPass
    guardPass -= 1
  print(checksum)