题目描述

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

输入格式

Each test contains multiple test cases.

The first line contains one positive integer t (1≤t≤104), 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≤l≤r≤109).

输出格式

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

样例

4 
1 1 
999999999 1000000000 
8 26 
1 999999999 

0 
1 
12 
499999999 

提示

In the first test case, the only allowed pair is (a,b)=(1,1), for which amodb=1mod1=0.

In the second test case, the optimal choice is pair (a,b)=(1000000000,999999999), for which amodb=1. 原题链接:https://codeforces.com/contest/1562/problem/A Qlu_Sp9rk1e55转录