The Miracle and the Sleeper

题意翻译

对给定区间 $[l,r]$，$1\le l \le r \le 10^9$ 求区间内的两个数 $a,b$，$b \le a$ 使得$a \bmod b$的值最大，并输出这个值。 输入一行一个数 $t$，$t\le10^4$表示样例个数。接下来 $t$ 行，每行两个数 $l$、$r$，表示一次询问。 输出分 $t$ 行表示每个询问的答案。

题目描述

You are given two integers $ l $ and $ r $ , $ l\le r $ . Find the largest possible value of $ a \bmod b $ over all pairs $ (a, b) $ of integers for which $ r\ge a \ge b \ge l $ . As a reminder, $ a \bmod b $ is a remainder we get when dividing $ a $ by $ b $ . For example, $ 26 \bmod 8 = 2 $ .

输入输出格式

输入格式

Each test contains multiple test cases. The first line contains one positive integer $ t $ $ (1\le t\le 10^4) $ , denoting the number of test cases. Description of the test cases follows. The only line of each test case contains two integers $ l $ , $ r $ ( $ 1\le l \le r \le 10^9 $ ).

输出格式

For every test case, output the largest possible value of $ a \bmod b $ over all pairs $ (a, b) $ of integers for which $ r\ge a \ge b \ge l $ .

输入输出样例

输入样例 #1

4
1 1
999999999 1000000000
8 26
1 999999999

输出样例 #1

0
1
12
499999999

说明

In the first test case, the only allowed pair is $ (a, b) = (1, 1) $ , for which $ a \bmod b = 1 \bmod 1 = 0 $ . In the second test case, the optimal choice is pair $ (a, b) = (1000000000, 999999999) $ , for which $ a \bmod b = 1 $ .