Find the Mother vertex in a directed graph. A mother vertex in a graph G = (V,E) is a vertex v such that all other vertices in G can be reached by a path from v.
The first line of input contains an integer T. Then T test cases follow. Each test case contains two integers N and M. In the next line are M space separated values u,v denoting an edge from u to v.
Output: For each testcase return the mother vertex of graph (if existes) else return -1.
Note: This is a functional probem. Complete function findmother().
1 <= T <= 100
1 <= N, M <= 104
0 <= u, v < N
1 0 0 2 2 1 0 3 3 4
0 1 2 1
Testcase 1: According to the given edges, all nodes can be reaced from nodes from 0, 1 and 2. But, since we are traversing from node 0, so 0 is the output.
Testcase 2: According to the given edges, no vertices are there from where we can reach all vertices. So, output is -1.
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