t = int(input().strip()) for _ in range(t): n, m = map(int, input().split()) if m < n or m > 5 * n: print(0) else: z_min = max(0, (m - 2 * n + 2) // 3) z_max = (m - n) // 4 print(max(0, z_max - z_min + 1))