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.* ;
  import java.util.* ;
  
  
   
  public class App {
      public static void main (String[] args) throws java.lang.Exception {
  		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
          //reader = new BufferedReader(new FileReader(new File("C:\\Users\\Anjali\\Desktop\\projects\\HelloWorld\\src\\input.txt")));
  		BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
         // writer = new BufferedWriter(new FileWriter(new File("C:\\Users\\Anjali\\Desktop\\projects\\HelloWorld\\src\\output.txt")));
  		//int tests = Integer.parseInt(reader.readLine());
          int tests = 1;
  		//StringBuilder sb = new StringBuilder(tests);
  		while (tests-- > 0){
  		    solve(reader, writer);
              writer.write("\n");
  		}
  		reader.close();
          writer.flush();
          writer.close();
      }
  
   
      static void solve(BufferedReader reader, BufferedWriter writer) throws  IOException {
  		int tests = Integer.parseInt(reader.readLine());
  		for (int i = 0; i < tests; i++) {
  			String[] input = reader.readLine().split(" ");
  			long l = Long.parseLong(input[0]);
  			long r = Long.parseLong(input[1]);
  			long ans = 0;
  			if (l <= (r / 2) + 1) {
  				ans = (r - 1) / 2;
  			} else {
  				ans = r - l;
  			}
  			writer.write(ans + "\n");
  		}	
  	}
  }
  