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 jdk.jfr.SettingControl;
  
  import java.io.*;
  import java.util.*;
  
  public class A {
  	static class InputReader {
  		BufferedReader reader;
  		StringTokenizer tokenizer;
  		public InputReader(InputStream stream) {
  			reader = new BufferedReader(new InputStreamReader(stream), 32768);
  			tokenizer = null;
  		}
  		String next() {
  			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
  				try {
  					tokenizer = new StringTokenizer(reader.readLine());
  				} catch (IOException e) {
  					throw new RuntimeException(e);
  				}
  			}
  			return tokenizer.nextToken();
  		}
  		public int ni() {
  			return Integer.parseInt(next());
  		}
  		public long nl() {
  			return Long.parseLong(next());
  		}
  		public double nd() {
  			return Double.parseDouble(next());
  		}
  		
  		public int[] ra(int n ) {
  			int[] a = new int[n];
  			for (int i = 0; i < n; i++) {
  				a[i] = r.ni();
  			}
  			return a;
  		}
  	}
  	
  	public static void sort(int[] a) {
  		List<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);
  		}
  	}
  	
  	public static void sortL(long[] a) {
  		List<Long> l = new ArrayList<>();
  		for (long i: a) {
  			l.add(i);
  		}
  		Collections.sort(l);
  		for (int i = 0; i < a.length; i++) {
  			a[i] = l.get(i);
  		}
  	}
  	
  	static InputReader r = new InputReader(System.in);
  	static PrintWriter pw = new PrintWriter(System.out);
  	public static void main(String[] args) {
  		int TT = r.ni();
  		while (TT-- > 0) {
  			long a = r.nl(), b = r.nl();
  			pw.println(b % Math.max(a, (b + 2) / 2));
  		}
  		pw.close();
  	}
  }
  