Path

In an undirected graph is required to find a minimal path between two vertices.

Input

In the input file is written first, the number N - the number of vertices in the graph (1 ≤ N ≤ 100). Then write the adjacency matrix (0 denotes the absence of ribs, 1 - presence of an edge). Then write the number two peaks - the start and end.

Output

The output display file L - length of the shortest path (number of edges that need to go). If the path does not exist, output a single number -1.

Examples