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No.2851 Make Pairs

レベル : / AI推定難易度 : 143 / 実行時間制限 : 1ケース 2.000秒 / メモリ制限 : 512 MB / 標準ジャッジ問題
タグ : （AC するまで非表示） / 解いたユーザー数 157
作問者 : dyktr_06 / テスター : ryota2357
お気に入りにしたユーザー ProblemId : 11300 / 自分の提出
問題文最終更新日: 2024-08-21 21:37:32
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yukicoder contest 442 MMA Contest 019 (順位表) の他の問題:

Problem Statement

$N$ cards are arranged in a row, and the $i$-th card from the left has the number $A_i$ written on it.

You may perform the following operation any number of times.

  • Choose $2$ cards with the same number written on them and erase those cards.

Find the maximum number of operations you can perform.

Constraints

  • $1 \leq N \leq 2 \times 10^5$
  • $1 \leq A_i \leq N$
  • All inputs are integers.

Input

The input is given from standard input in the following format.

$N$
$A_1$ $A_2$ ... $A_{N}$

Output

Print the answer to the problem on one line.

Sample

Sample 1
Input
5
1 2 3 1 2
Output
2

You can perform the operations as follows.

  • Choose the $1$-st and $4$-th cards from the left and erase them.
  • Choose the $2$-nd and $5$-th cards from the left and erase them.

It is impossible to perform more than $2$ operations, so print $2$.

Sample 2
Input
10
1 2 3 4 5 6 7 8 9 8
Output
1

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