Choose and Divide

Time Limit: 2 Seconds
Memory Limit: 65536 KB

The binomial coefficient C(m,n) is defined as

m!

C(m,n) = --------

n!(m-n)!

Given four natural numbers p, q, r, and s, compute the the result of dividing
C(p,q) by C(r,s).

**Input**

Input consists of a sequence of lines. Each line contains four non-negative
integer numbers giving values for p, q, r, and s, respectively, separated by
a single space. All the numbers will be smaller than 10,000 with p>=q and
r>=s.

**Output**

For each line of input, print a single line containing a real number with 5
digits of precision in the fraction, giving the number as described above. You
may assume the result is not greater than 100,000,000.

**Sample Input**

10 5 14 9

93 45 84 59

145 95 143 92

995 487 996 488

2000 1000 1999 999

9998 4999 9996 4998

**Sample Output**

0.12587

505606.46055

1.28223

0.48996

2.00000

3.99960

Source:

**University of Waterloo Local Contest 1999.10.02**
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