Unweighted Paths on NetworkX X25538

networkx

Given a directed graph with n vertices and m arcs, we wish to know if there is a directed path between two given vertices.

Input

Input starts with n and m. Then follow m pairs u,v, with u ≠ v, indicating an arc from u to v. We have that 0 ≤ u < n and 0 ≤ v < n and that there are no repeated arcs. Then follows a pair x, y with 0 ≤ x < n and 0 ≤ y < n.

Output

Write “yes” or “no” according to whether there is a path from x to y.

Observation

We are authorized to employ the NetworkX library.