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: def solve(Test_cases):
      Resultant_list = []
      for i in range(Test_cases):
          # Start the code
          string = input()
          list_me = list(string.split())
          map_object = map(int, list_me)
          list_me = list(map_object)
          l, r = list_me[0], list_me[1]
  
          if r == l:
              Resultant_list.append(0)
          elif r % 2 != 0:
              # r is odd
              value_1 = (r + 1) // 2
              if value_1 >= l:
                  Resultant_list.append(r % value_1)
              else:
                  Resultant_list.append(r % l)
          else:
              # r is even
              value_2 = (r // 2) + 1
              if value_2 >= l:
                  Resultant_list.append(r % value_2)
              else:
                  Resultant_list.append(r % l)
      return Resultant_list
  
  
  Test_cases = int(input())
  if Test_cases < 1 or Test_cases > pow(10, 4):
      exit()
  Result = solve(Test_cases)
  for i in Result:
      print(i)
  