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题目描述

Given a directed graph, a K-vertex is a vertex of which the out degree is larger than the indegree. For example, the vertices a and b in the figure are K-vertices.

Your job is to list all the K-vertices in a given graph.

输入格式

Each input file contains one test case. For each case, the first line contains 2 positive integers: $N$ ($\le 200$) and $M$, which are the number of vertices and the number of edges, respectively. Then $M$ lines follow, each gives a directed edge < v1 , v2 > in the format:

v1 v2

Here we assume that all the vertices are numbered from $0$ to $N-1$. It is guaranteed that v1 is never the same as v2.

Finally a line of $N$ strings is given, where the $i$-th string corresponds to the key of the $i$-th vertex ($i=0, \cdots , N-1$). Each string consists of no more than 2 lower-cased English letters.

输出格式

Output the keys of all the K-vertices, each occupies a line, in alphabetical order. It is guaranteed that there is at least one output.

样例

4 5
0 1
2 1
3 1
2 0
3 2
c d b a

a
b

限制

Java (javac) 时间限制 900 ms 内存限制 256 MB

其他编译器 时间限制 400 ms 内存限制 64 MB