发下原题和本人渣翻
498. Coins
                                  498.硬币
Time limit per test: 0.75 second(s)
每次测试时间限定：0.75s
Memory limit: 262144 kilobytes
限定内存：262144 kilobytes
input: standard
output: standard
标准输入输出

Andrew has just made a breakthrough in gambling: he has invented a way to make coins which have probability p of landing heads-up and 1 - p of landing tails-up when tossed, where p is some number between 0 and 1.
Andrew近来在赌博上取得重大突破：他发明了一种方法来赚取硬币，就是那种在投掷时有p的概率正面朝上和1-p的概率反面朝上的硬币，p是某个在0和1之间的数。
He can't, however, control the number p itself, and creates coins with any p from 0 to 1 with equal probability.
然而，他并不能控制概率p本身，并等可能的创造概率p从0到1变化的硬币。
 That is, the value of p is a random value uniformly distributed on  .
也就是说，p的值是一个在0到1之间随机分布的数。
Andrew has generated two coins independently.
Andrew已经互相独立地准备了两枚硬币。
One with probability p and another with probability q of landing heads-up.
一枚朝上的概率为p，另一枚为q。
Random values p and q are both uniformly distributed on  and are independent.
随机值p和q都分布在0至1之间并相互独立。
Of course, neither Andrew nor we know the numbers p and q, we can only try to guess them using our observations.
自然，不论是Andrew还是我们都不知道p和q的值，我们只能通过我们的观察来进行猜测。
The observations are the following: the first coin was tossed n1 times, and m1 of them landed heads-up. The second coin was tossed n2 times, and m2 of them landed heads-up. Your task is to compute the probability that p < q.
观测方法如下：第一枚硬币被投掷n1次，并有m1次正面朝上。第二枚硬币被投掷n2次，并有m2次正面朝上。你的任务是计算出p<q的概率。
Input
The first line of the input file contains one integer T ( ) — the number of test cases to solve. Each of the following T lines contains 4 integers each: n1, m1, n2, m2. 1 ≤ n1, n2 ≤ 1000, 0 ≤ m1, m2 ≤ 50, 0 ≤ m1 ≤ n1, 0 ≤ m2 ≤ n2.
第一行输入包含一个整数T ( )，即测试用例的数，在T行下的每一行包含4个整数，分别为：n1,m1,n2,m2. 1 ≤ n1, n2 ≤ 1000, 0 ≤ m1, m2 ≤ 50, 0 ≤ m1 ≤ n1, 0 ≤ m2 ≤ n2.

Output
For each test case output one line with a floating-point number, the probability of p < q. Your answer will be considered correct if it is within 10-4 of the right answer.
每次测试用例输出一个浮点数，即p<q的概率。你的结果将被认为正确如果它与正确答案相差不超过10-4
Example(s)
sample input    sample output
4
2 1 4 3     0.7142857142
8 4 16 8    0.5000000000
2 0 6 1     0.5333333333
2 0 2 1     0.8000000000