Cleaning Up runtime error

Hi,
I was trying out Clean Up problem from Practice section, but this code I wrote is giving me an NZEC. I have no idea why.

Code:

from __future__ import division
def read_mapped(func=lambda x:x):
    return map(func, raw_input().strip().split(" "))
def read_int():
    return int(raw_input().strip())
def read_str():
    return raw_input().strip()
def read_float():
    return float(raw_input().strip())

T = read_int()

for case in xrange(T):
    n, m = read_mapped(int)
    lis = range(1, n+1)
    jobs = read_mapped(int) if m!=0 else []

    for j in jobs:
        lis.remove(j)

    chef = []
    assistant = []
    for i, index in enumerate(lis):
        if i%2==0:
            assistant.append(str(index))
        else:
            chef.append(str(index))

    print "" if not assistant else " ".join(assistant)
    print "" if not chef else " ".join(chef)

I've tried all test cases I could imagine, it works fine. Please tell me why this is giving me an NZEC.

Thanks.