Preparando MOJI
International Women's Day is coming soon! Polycarp is preparing for the holiday.
There are $$$n$$$ candy boxes in the shop for sale. The $$$i$$$-th box contains $$$d_i$$$ candies.
Polycarp wants to prepare the maximum number of gifts for $$$k$$$ girls. Each gift will consist of exactly two boxes. The girls should be able to share each gift equally, so the total amount of candies in a gift (in a pair of boxes) should be divisible by $$$k$$$. In other words, two boxes $$$i$$$ and $$$j$$$ ($$$i \ne j$$$) can be combined as a gift if $$$d_i + d_j$$$ is divisible by $$$k$$$.
How many boxes will Polycarp be able to give? Of course, each box can be a part of no more than one gift. Polycarp cannot use boxes "partially" or redistribute candies between them.
The first line of the input contains two integers $$$n$$$ and $$$k$$$ ($$$1 \le n \le 2 \cdot 10^5, 1 \le k \le 100$$$) — the number the boxes and the number the girls.
The second line of the input contains $$$n$$$ integers $$$d_1, d_2, \dots, d_n$$$ ($$$1 \le d_i \le 10^9$$$), where $$$d_i$$$ is the number of candies in the $$$i$$$-th box.
Print one integer — the maximum number of the boxes Polycarp can give as gifts.
7 2 1 2 2 3 2 4 10
6
8 2 1 2 2 3 2 4 6 10
8
7 3 1 2 2 3 2 4 5
4
In the first example Polycarp can give the following pairs of boxes (pairs are presented by indices of corresponding boxes):
So the answer is $$$6$$$.
In the second example Polycarp can give the following pairs of boxes (pairs are presented by indices of corresponding boxes):
So the answer is $$$8$$$.
In the third example Polycarp can give the following pairs of boxes (pairs are presented by indices of corresponding boxes):
So the answer is $$$4$$$.
Informação
Provedor Codeforces
Código CF1133B
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Datas 09/05/2023 09:45:37
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