## Problem D: Choose and divide

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)`.
### The 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`.
### The 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

### Output for Sample Input

0.12587
505606.46055
1.28223
0.48996
2.00000
3.99960