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 bisect
  import math
  
  mod =  998244353
  N = 200005
  
  def mul(a, b):
  	return (a*b)%mod
  
  def add(a, b):
  	return (a+b) if (a+b<mod) else (a+b)-mod
  
  def sub(a, b):
  	return (a-b) if (a-b>0) else (a-b)+mod
  
  def powr(a, b):
  	ans = 1
  	while b>0:
  		if b & 1:
  			ans=mul(ans,a)
  		a = mul(a,a) 
  		b//=2
  	return ans
  
  def inv(n):
  	return powr(n, mod-2)
  
  def factlist():
  	fact = [1]
  	for i in range(1, N):
  		fact.append(mul(fact[i-1],i))
  	return fact
  
  def invfactlist(fact):
  	invfact=[0]*N
  	invfact[0]=1
  	invfact[N-1]= inv(fact[N-1])
  	for i in range(N-2, 0, -1):
  		invfact[i]= mul(invfact[i+1],(i+1))
  	
  	return invfact
  
  def rot(S):
  	return list(zip(*S[::-1]))
  
  def gcd(a, b):
  	if b==0:
  		return a
  	return gcd(b, a%b)
  
  
  def main():
  	t = int(input())
  	while t:
  		t-=1 
  
  		l, r = map(int, input().split())
  		if l == r:
  			print('0')
  			continue
  		if l>(r+1)//2:
  			print(r-l)
  			continue
  		else:
  			k = (r+1)//2
  			print(k-1)
  
  	
  
  if __name__ == "__main__":
  	main()
  	
  