__
Chocolate Box__

**Input:** standard input

**Output:** standard output

**Time Limit:** 1 second

Recently one of my friend Tarik became a member of the food committee
of an ACM regional competition. He has been given m distinguishable
boxes, he has to put n types of chocolates in the boxes. The
probability that one chocolate is placed in a certain box is 1 / m.
What is the probability that one or more boxes are empty?

__Input__

Each line of the input contains
two integers **n** indicating total number of distinguishable types
of chocolate and **m** indicating total number of distinguishable
boxes **( m <= n < 100 )**. A single line containing *
-1* denotes the end.

For each of the cases you should calculate the probability corrected to seven decimal places. The output format is shown below.

__Sample Input__

50 12

50 12

-1

__Sample
Output__

Case 1: 0.1476651

Case 2: 0.1476651

Problem Setter: A. K. M. Saifun Nabi (Shabuj) ( BUET PESSIMISTIC )

Thanks to Anupam Bhattacharjee for his alternate solution and data.