SUMFOUR  4 values whose sum is 0
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
Input
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
Output should be printed on a single line.
Example
Input: 6 45 22 42 16 41 27 56 30 36 53 37 77 36 30 75 46 26 38 10 62 32 54 6 45 Output: 5
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abhinav_jain02:
20190518 08:28:58
Note that equal elements in a list are considered to be distinct 

mikroz:
20190413 13:19:50
gp_hash_table 

sagar_june97p:
20190412 20:07:25
unordered_map got me TLE, however equal_range passed.


prudhvi_495:
20190407 13:20:45
Last edit: 20190414 08:06:25 

syed_tanveer:
20190403 12:40:58
AC in first go using upper_bound() and lower_bound() 

Rahul Kathuria:
20190403 03:44:13
Easy peasy :P AC in 1st go!


divik544:
20190327 15:51:02
1. Do not remove duplicates.


y17prashant:
20190322 02:30:56
use vectors , array gave a RE.......fast io worked here .....Hint Complexity O(n^2*log(k))........Simple one Last edit: 20190322 02:33:16 

alphacoder101:
20190206 05:31:00
This is what happened for me:


masterchef2209:
20181017 22:57:20
unordered_map with reserve keyword got accepted

Added by:  Abhilash I 
Date:  20070206 
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