A Plug for UNIX 最大流 建图
You are in charge of setting up the press room for the inaugural meeting of the United Nations Internet eXecutive (UNIX), which has an international mandate to make the free flow of information and ideas on the Internet as cumbersome and bureaucratic as possible.
Since the room was designed to accommodate reporters and journalists from around the world, it is equipped with electrical receptacles to suit the different shapes of plugs and voltages used by appliances in all of the countries that existed when the room was built. Unfortunately, the room was built many years ago when reporters used very few electric and electronic devices and is equipped with only one receptacle of each type. These days, like everyone else, reporters require many such devices to do their jobs: laptops, cell phones, tape recorders, pagers, coffee pots, microwave ovens, blow dryers, curling
irons, tooth brushes, etc. Naturally, many of these devices can operate on batteries, but since the meeting is likely to be long and tedious, you want to be able to plug in as many as you can.
Before the meeting begins, you gather up all the devices that the reporters would like to use, and attempt to set them up. You notice that some of the devices use plugs for which there is no receptacle. You wonder if these devices are from countries that didn’t exist when the room was built. For some receptacles, there are several devices that use the corresponding plug. For other receptacles, there are no devices that use the corresponding plug.
In order to try to solve the problem you visit a nearby parts supply store. The store sells adapters that allow one type of plug to be used in a different type of outlet. Moreover, adapters are allowed to be plugged into other adapters. The store does not have adapters for all possible combinations of plugs and receptacles, but there is essentially an unlimited supply of the ones they do have.
Input
The input will consist of one case. The first line contains a single positive integer n (1 <= n <= 100) indicating the number of receptacles in the room. The next n lines list the receptacle types found in the room. Each receptacle type consists of a string of at most 24 alphanumeric characters. The next line contains a single positive integer m (1 <= m <= 100) indicating the number of devices you would like to plug in. Each of the next m lines lists the name of a device followed by the type of plug it uses (which is identical to the type of receptacle it requires). A device name is a string of at most 24 alphanumeric
characters. No two devices will have exactly the same name. The plug type is separated from the device name by a space. The next line contains a single positive integer k (1 <= k <= 100) indicating the number of different varieties of adapters that are available. Each of the next k lines describes a variety of adapter, giving the type of receptacle provided by the adapter, followed by a space, followed by the type of plug.
Output
A line containing a single non-negative integer indicating the smallest number of devices that cannot be plugged in.
Sample Input
4
A
B
C
D
5
laptop B
phone C
pager B
clock B
comb X
3
B X
X A
X D
Sample Output
1
现在有N种插头，M种设备，每种设备对应一种插头(插头与插座编号一致的时候，表示对应)，还有K种插头转换器，每个插头转化器有无限个可以用，现在问多少有多少设备接不上插座。
我们可以用图来表示实际操作上的逻辑关系。首先，设备和设备插头的种类有一个对应关系，所以建一条边在设备与插头种类上，容量为1，因为一个设备只有一个插头。之后，插头和对应的插座连边，表示插头插入插座中，容量为1，同样因为一个插座只能插一个插头。这样一台设备连接电源就在图中实现了。
现在再考虑插头转化器在图中的实现，假设现在有一个插头转换器，它有一个A类型插口和B类型插头，可以把A插头转换为B插头插到B插座中，简单一点说就是，这个插头转换器可以把A插头变为B插头，反应到图中，就可以在A插头与B插头之间连一条容量为无穷的边表示这个转换关系，容量无穷大是因为插头转换器使用没有限制。
最后源点与设备，插座与汇点连边，跑一下最大流就是最多能有多少设备可以连到插座上，减去设备总数就是最少有多少设备连不到插座上。
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