Given an undirected graph. Find the shortest distance from one given vertex to another.

Input

First line contains three positive integers n, s and f (1 ≤ s, f ≤ n ≤ 100) - the number of vertices in the graph and the number of initial and final vertices. Next n lines describe the adjacency matrix of the graph. If the value of the j-th element of the i-th row is 1, then the graph has a directed edge from vertex i to vertex j.

Output

Print the minimum distance from the initial to final vertex. If path does not exist, print 0.