C(m,n) = m! (m − n)! 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 frac- tion, 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