CF225D Snake

Let us remind you the rules of a very popular game called "Snake" (or sometimes "Boa", "Python" or "Worm"). The game field is represented by an $ n×m $ rectangular table. Some squares of the field are considered impassable (walls), all other squares of the fields are passable. You control a snake, the snake consists of segments. Each segment takes up exactly one passable square of the field, but any passable square contains at most one segment. All segments are indexed by integers from $ 1 $ to $ k $ , where $ k $ is the snake's length. The $ 1 $ -th segment is the head and the $ k $ -th segment is the tail. For any $ i $ ( $ 1

The first line contains two space-separated integers $ n $ and $ m $ ( $ 1

Print a single integer to the output — the minimum number of moves needed to reach the apple. If the snake can't reach the apple, print -1.