Competitions

# Breadth First Search - Introduction

# Breadth First Search

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**.

Input example #1

4 4 3 0 1 1 1 1 0 1 0 1 1 0 0 1 0 0 0

Output example #1

2