Breadth First Search

Given an undirected graph. Find the shortest distance between two specified vertices.

Input

The first line contains three positive integers $n,s$ and $f(1\le s,f\le n\le 100)$. Here, $n$ is the number of vertices in the graph, $s$ and $f$ are the initial and final vertices. The next $n$ lines provide the adjacency matrix of the graph. If the value at the $j$-th element of the $i$-th row is $1$, there is an edge between vertex $i$ and vertex $j$.

Output

Print the minimum distance from the initial vertex to the final vertex. If no path exists, print $0$.

Examples