def bin_search2(arr,value, left, right):
  mid = int((left + right) / 2)
  guess = arr[mid]
  if guess == value:
    return mid
  if guess < value:
    left = mid + 1
    return bin_search2(arr,value, left, right)
  if guess > value:
    right = mid - 1
    return bin_search2(arr,value, left, right)
  return None