class Solution(object):
def fourSumCount(self, A, B, C, D):
"""
:type A: List[int]
:type B: List[int]
:type C: List[int]
:type D: List[int]
:rtype: int
"""
AB=collections.Counter(a+b for a in A for b in B)
return sum(AB[-c-d] for c in C for d in D)
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