Traceback (most recent call last):
  File "/usr/lib/python3.6/py_compile.py", line 125, in compile
    _optimize=optimize)
  File "<frozen importlib._bootstrap_external>", line 741, in source_to_code
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/w/foo.py", line 4
    for b in range(1,l-a):
      ^
IndentationError: expected an indented block

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.6/py_compile.py", line 129, in compile
    raise py_exc
py_compile.PyCompileError: Sorry: IndentationError: expected an indented block (foo.py, line 4)

[Hydro](https://hydro.ac)提供评测服务