Directed unweighted graph is given. Find in it a vertex, the shortest distance from which to the given one is maximum, and print this distance. \InputFile First line contains three positive integers $n, m$ и $s~(1 \le s \le n \le 5000, 1 \le m \le 20000)$ --- the number of vertices and edges in the graph and the number of given vertex. In the next $m$ lines the graph edges are given. Each edge is given with the pair of numbers --- the starting and the ending point. \OutputFile Print the required shortest distance. \includegraphics{https://static.e-olymp.com/content/f4/f4772aaa6b8bd838830cab6e402cccd434ef452c.gif}