A11473. Magic Forest
编程题
普及/提高-
知识点
题目描述
Imp is in a magic forest, where xorangles grow (wut?)
A xorangle of order $n$ is such a non-degenerate triangle, that lengths of its sides are integers not exceeding $n$ , and the xor-sum of the lengths is equal to zero. Imp has to count the number of distinct xorangles of order $n$ to get out of the forest.
Formally, for a given integer $n$ you have to find the number of such triples $(a,b,c)$ , that:
- $1<=a<=b<=c<=n$ ;
- , where  denotes the [bitwise xor](https://en.wikipedia.org/wiki/Bitwise_operation#XOR) of integers $x$ and $y$ .
- $(a,b,c)$ form a non-degenerate (with strictly positive area) triangle.
A xorangle of order $n$ is such a non-degenerate triangle, that lengths of its sides are integers not exceeding $n$ , and the xor-sum of the lengths is equal to zero. Imp has to count the number of distinct xorangles of order $n$ to get out of the forest.
Formally, for a given integer $n$ you have to find the number of such triples $(a,b,c)$ , that:
- $1<=a<=b<=c<=n$ ;
- , where  denotes the [bitwise xor](https://en.wikipedia.org/wiki/Bitwise_operation#XOR) of integers $x$ and $y$ .
- $(a,b,c)$ form a non-degenerate (with strictly positive area) triangle.
输入格式
The only line contains a single integer $n$ $(1<=n<=2500)$ .
输出格式
Print the number of xorangles of order $n$ .
输入输出样例
输入 #1
6
输出 #1
1
输入 #2
10
输出 #2
2
说明/提示
The only xorangle in the first sample is $(3,5,6)$ .