SUMFOUR - 4 values whose sum is 0

给定4个数列A,B,C,D。要从每个数列中取出1个数，使4个数的和为0。求出这样的组合个数。当一个数列中有多个相同的数字时，把他们作为不同的数字看待。 输入： 第一行：n 以下n行，每行4个数，第i行为ai,bi,ci,di。 输出： 组合数个数。 限制： n<=4000; |ai,bi,ci,di|<=2^28

The SUM problem can be formulated as follows: given four lists A, B, C, D of integer values, compute how many quadruplet (a, b, c, d ) belongs to A x B x C x D are such that a + b + c + d = 0 . In the following, we assume that all lists have the same size n

The first line of the input file contains the size of the lists n (this value can be as large as 4000). We then have n lines containing four integer values (with absolute value as large as 2 $ ^{28} $ ) that belong respectively to A, B, C and D . (**Edited:** n <= 2500)

Output should be printed on a single line.

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-45 22 42 -16
-41 -27 56 30
-36 53 -37 77
-36 30 -75 -46
26 -38 -10 62
-32 -54 -6 45

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