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题库练习 Powers of Two

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A10525 | $Powers of Two$

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题目描述

You are given $n$ integers $a_{1},a_{2},...,a_{n}$ . Find the number of pairs of indexes $i,j$ ( $i<j$ ) that $a_{i}+a_{j}$ is a power of $2$ (i. e. some integer $x$ exists so that $a_{i}+a_{j}=2^{x}$ ).

输入格式

The first line contains the single positive integer $n$ ( $1<=n<=10^{5}$ ) — the number of integers. The second line contains $n$ positive integers $a_{1},a_{2},...,a_{n}$ ( $1<=a_{i}<=10^{9}$ ).

输出格式

Print the number of pairs of indexes $i,j$ ( $i<j$ ) that $a_{i}+a_{j}$ is a power of $2$ .

输入输出样例

输入 #1

4
7 3 2 1

输出 #1

输入 #2

3
1 1 1

输出 #2

C++ 编辑器

输入

输出