Factorials

PROBLEM STATEMENT
Given a number n and a base b, return the largest power of b that divides n
factorial.

DEFINITION
Class: Factorials
Paramenters: int, int
Returns: int
Method signature (be sure your method is public): int largestPower(int n, int b);

NOTES
TopCoder will ensure the validity of the inputs.  Inputs are valid if all of
the following criteria are met:
- n will be between 1 and 50 inclusive.
- b will be between 2 and 29 inclusive.

EXAMPLES
1.  If n = 5, and b = 2.  
-  5! = 120 = 2^3 * 15.  Return 3.

2.  If n = 7, and b = 5.
-  7! = 5040 = 5^1 * 1008.  Return 1.

3.  If n = 11, and b = 3.
-  11! = 39916800 = 3^4 * 492800.  Return 4.

Notes to admins:
This problem gets tough for bigger numbers where n! is greater than
Integer.MAX_VALUE.  The solution is pretty simple when b is prime in that case,
but when b is composite it gets tricky.