When you rent a table at a pool hall, the proprietor gives you a 4-by-4 tray of 16 balls, as shown
in Figure (a) below. One of these balls, called the “cue ball”, is white, and the remaining 15 are
numbered 1 through 15. At the beginning of a game, the numbered balls are racked up in a
triangle (without the cue ball), as shown in Figure (b).
(a) (b)
Now imagine other pool-like games where you have a cue ball and x numbered balls. You’d like
to be able to rack up the x numbered balls in a triangle, and have all x+1 balls perfectly fill a
square m-by-m tray. For what values of x is this possible? In this problem you’ll be given an lower
bound a and upper bound b, and asked how many numbers within this range have the above
property.
Input
Input for each test case will one line containing two integers a b, where 0 < a < b ≤ 109
The line 0 0 will follow the last test case.
Output
For each test case one line of output as follows: Case n: k
if there are k integers x such that a < x+1 < b, x balls can be racked up in a triangle, and x+1 balls
fill a square tray.
Sample Input/Output