Margarite and the best present

题意翻译

### 题目描述 小女孩Margarita是信息竞赛的忠实粉丝，她对数组和数列问题尤其感兴趣。 最近，她提出了一个长度为$10^9$的数列： $a_1=-1$ $a_2=2$ $a_3=-3$ $a_4=4$ $a_5=-5$ $\cdots$ 同样的，它也可以被表示成下面这个样子： $$ a_i=i*(-1)^i,1\le i \le 10^9 $$ Margarita提出了$q$个询问，每一个询问包含两个整数：$l$和$r$。对于每一个询问，你需要回答$\sum_{i=l}^{r}a_i$的值，即数列中第$l$项至第$r$项的和。 ### 输入格式： 第一行包含一个整数$q$，表示询问的组数。 接下来$q$行每行包含两个整数$l$和$r$，表示每一组询问。 ### 输出格式： 输出$q$行，表示每个询问的答案。 ### 说明： 第一个询问中，你需要回答第$1$项至第$3$项的和，$a_1+a_2+a_3=-1+2-3=-2$。 第二个询问中，你需要回答第$2$项至第$5$项的和，$a_2+a_3+a_4+a_5=2-3+4-5=-2$。 第三个询问中，你需要回答第$5$项至第$5$项的和，$a_5=-5$。 第四个询问中，你需要回答第$4$项至第$4$项的和，$a_4=4$。 第五个询问中，你需要回答第$2$项至第$3$项的和，$a_2+a_3=2-3=-1$。

题目描述

Little girl Margarita is a big fan of competitive programming. She especially loves problems about arrays and queries on them. Recently, she was presented with an array $ a $ of the size of $ 10^9 $ elements that is filled as follows: - $ a_1 = -1 $ - $ a_2 = 2 $ - $ a_3 = -3 $ - $ a_4 = 4 $ - $ a_5 = -5 $ - And so on ... That is, the value of the $ i $ -th element of the array $ a $ is calculated using the formula $ a_i = i \cdot (-1)^i $ . She immediately came up with $ q $ queries on this array. Each query is described with two numbers: $ l $ and $ r $ . The answer to a query is the sum of all the elements of the array at positions from $ l $ to $ r $ inclusive. Margarita really wants to know the answer to each of the requests. She doesn't want to count all this manually, but unfortunately, she couldn't write the program that solves the problem either. She has turned to you — the best programmer. Help her find the answers!

输入输出格式

输入格式

The first line contains a single integer $ q $ ( $ 1 \le q \le 10^3 $ ) — the number of the queries. Each of the next $ q $ lines contains two integers $ l $ and $ r $ ( $ 1 \le l \le r \le 10^9 $ ) — the descriptions of the queries.

输出格式

Print $ q $ lines, each containing one number — the answer to the query.

输入输出样例

输入样例 #1

5
1 3
2 5
5 5
4 4
2 3

输出样例 #1

-2
-2
-5
4
-1

说明

In the first query, you need to find the sum of the elements of the array from position $ 1 $ to position $ 3 $ . The sum is equal to $ a_1 + a_2 + a_3 = -1 + 2 -3 = -2 $ . In the second query, you need to find the sum of the elements of the array from position $ 2 $ to position $ 5 $ . The sum is equal to $ a_2 + a_3 + a_4 + a_5 = 2 -3 + 4 - 5 = -2 $ . In the third query, you need to find the sum of the elements of the array from position $ 5 $ to position $ 5 $ . The sum is equal to $ a_5 = -5 $ . In the fourth query, you need to find the sum of the elements of the array from position $ 4 $ to position $ 4 $ . The sum is equal to $ a_4 = 4 $ . In the fifth query, you need to find the sum of the elements of the array from position $ 2 $ to position $ 3 $ . The sum is equal to $ a_2 + a_3 = 2 - 3 = -1 $ .