Competitions

# 9 Round Spiral. Round 1. Step 9.

# 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**.

Input example #1

2 0 1 1 0 1 2

Output example #1

1