Grid

Input

The first line contains two space-separated positive integers $m$ and $n$ (1 \le m, n \le 500). It is guaranteed that at least one of $m$ and $n$ is greater than $1$. The next $m$ lines each consists of $n$ digits, describing the m \times n grid. Each digit is between $0$ to $9$.

Output

Print, on a single line, a single integer denoting the minimum number of moves needed to get from the top-left corner to the bottom-right corner. If it is impossible to reach the bottom-right corner, print IMPOSSIBLE instead.

Examples