Dark Assembly

议会里有 n 个议员，每个议员有两个属性：级别和忠诚值。 现在你要在议会通过一个议案，一个议案通过当且仅当严格超过一半的议员投赞同票。一个议员投赞同票的几率就是忠诚值除以 100。 议员们有着奇怪的癖好：他们都喜欢吃糖。你带了K个糖果用来贿赂议员，每个糖果的作用是使得某个议员的忠诚值增加 10。贿赂要在投票开始前完成。（注意任意议员的忠诚值不可能大于 100） 投票之后，如果议案没有通过，你就会很暴力地把投了反对票的所有议员暗杀掉。假设你要暗杀的议员集合是 S，那么成功率就是 A/(A+B)；其中 A 是给定的常数，B 是 S 中所有议员级别的和。当暗杀成功后你的议案就会获得通过。 现在要求最优贿赂方案下最大的成功几率是多大。

Dark Assembly is a governing body in the Netherworld. Here sit the senators who take the most important decisions for the player. For example, to expand the range of the shop or to improve certain characteristics of the character the Dark Assembly's approval is needed. The Dark Assembly consists of $ n $ senators. Each of them is characterized by his level and loyalty to the player. The level is a positive integer which reflects a senator's strength. Loyalty is the probability of a positive decision in the voting, which is measured as a percentage with precision of up to $ 10% $ . Senators make decisions by voting. Each of them makes a positive or negative decision in accordance with their loyalty. If strictly more than half of the senators take a positive decision, the player's proposal is approved. If the player's proposal is not approved after the voting, then the player may appeal against the decision of the Dark Assembly. To do that, player needs to kill all the senators that voted against (there's nothing wrong in killing senators, they will resurrect later and will treat the player even worse). The probability that a player will be able to kill a certain group of senators is equal to $ A/(A+B) $ , where $ A $ is the sum of levels of all player's characters and $ B $ is the sum of levels of all senators in this group. If the player kills all undesired senators, then his proposal is approved. Senators are very fond of sweets. They can be bribed by giving them candies. For each received candy a senator increases his loyalty to the player by $ 10% $ . It's worth to mention that loyalty cannot exceed $ 100% $ . The player can take no more than $ k $ sweets to the courtroom. Candies should be given to the senators before the start of voting. Determine the probability that the Dark Assembly approves the player's proposal if the candies are distributed among the senators in the optimal way.

The first line contains three integers $ n $ , $ k $ and $ A $ ( $ 1<=n,k<=8 $ , $ 1<=A<=9999 $ ). Then $ n $ lines follow. The $ i $ -th of them contains two numbers — $ b_{i} $ and $ l_{i} $ — the $ i $ -th senator's level and his loyalty. The levels of all senators are integers in range from $ 1 $ to $ 9999 $ (inclusive). The loyalties of all senators are integers in range from $ 0 $ to $ 100 $ (inclusive) and all of them are divisible by $ 10 $ .

Print one real number with precision $ 10^{-6} $ — the maximal possible probability that the Dark Assembly approves the player's proposal for the best possible distribution of candies among the senators.

5 6 100
11 80
14 90
23 70
80 30
153 70

1.0000000000

5 3 100
11 80
14 90
23 70
80 30
153 70

0.9628442962

1 3 20
20 20

0.7500000000

In the first sample the best way of candies' distribution is giving them to first three of the senators. It ensures most of votes. It the second sample player should give all three candies to the fifth senator.