description: You are given two integers l and r, l≤ r. Find the largest possible value of a mod b over all pairs (a, b) of integers for which r≥ a ≥ b ≥ l.
  
  As a reminder, a mod b is a remainder we get when dividing a by b. For example, 26 mod 8 = 2.
  
  Input
  
  Each test contains multiple test cases.
  
  The first line contains one positive integer t (1≤ t≤ 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≤ l ≤ r ≤ 10^9).
  
  Output
  
  For every test case, output the largest possible value of a mod b over all pairs (a, b) of integers for which r≥ a ≥ b ≥ l.
  
  Example
  
  Input
  
  
  4
  1 1
  999999999 1000000000
  8 26
  1 999999999
  
  
  Output
  
  
  0
  1
  12
  499999999
  
  Note
  
  In the first test case, the only allowed pair is (a, b) = (1, 1), for which a mod b = 1 mod 1 = 0.
  
  In the second test case, the optimal choice is pair (a, b) = (1000000000, 999999999), for which a mod b = 1.
solution: 
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.StringTokenizer;
  
  public class Main {
  	
  	static FastScanner fs = new FastScanner();
  
  	public static void main(String[] args) {
  		
  		FastScanner fs = new FastScanner();
  		int test = fs.nextInt();
  		while(test-->0) {
  			int a = fs.nextInt(), b = fs.nextInt();
  //			int[] a = new int[n];
  //			for(int i=0 ; i<n ; i++) {
  //				a[i] = fs.nextInt();
  //			}
  			if(b/2+1>a) {
  				System.out.println(b%(b/2+1));
  			}else System.out.println(b%a);
  		}
  	}
  	
  	public static boolean check(int[] a) {
  		for(int i=0 ; i<a.length ; i++) {
  			if(a[i]!=i+1) return false;
  		}
  		return true;
  	}
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	public static int[] readArray(int n){
  		int[] a = new int[n];
  		for(int i=0 ; i<n ; i++) {
  			a[i] = fs.nextInt();
  		}
          return a;
      }
  	
  	public static void printArray(int[] n){
          for(int e:n) {
          	System.out.print(e + " ");
          }
          System.out.println();
      }
  	
  	static void sort(int[] a) {
  		ArrayList<Integer> l=new ArrayList<>();
  		for (int i:a) l.add(i);
  		Collections.sort(l);
  		for (int i=0; i<a.length; i++) a[i]=l.get(i);
  	}
  	
  	static class FastScanner {
  		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  		StringTokenizer st=new StringTokenizer("");
  		String next() {
  			while (!st.hasMoreTokens())
  				try {
  					st=new StringTokenizer(br.readLine());
  				} catch (IOException e) {
  					e.printStackTrace();
  				}
  			return st.nextToken();
  		}
  		
  		int nextInt() {
  			return Integer.parseInt(next());
  		}
  		int[] readArray(int n) {
  			int[] a=new int[n];
  			for (int i=0; i<n; i++) a[i]=nextInt();
  			return a;
  		}
  		String[] readStringArray(int n) {
  			String[] a=new String[n];
  			for (int i=0; i<n; i++) a[i]=next();
  			return a;
  		}
  		long nextLong() {
  			return Long.parseLong(next());
  		}
  	}
  	
  	
  
  }
  