P4629 - 2的幂 - ZUFEOJ

内存限制：256 MB 时间限制：2 S

题面：传统评测方式：文本比较上传者：

提交：64 通过：20

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Examples

Input

4
7 3 2 1

Output

Input

3
1 1 1

Output

Note

In the first example the following pairs of indexes include in answer: (1,4) and (2,4).
In the second example all pairs of indexes (i,j) (where i<j) include in answer.

4
7 3 2 1

cf702B 1500 brute force data structures implementation math 思维