Background:

$FWX$ is very adored of $Guan$ orz

Problem Description:

$FWX$ and $Guan$ live in a point a11 and amn in a rectangular town of size m * n (ensuring that they are on the same diagonal). Because $FWX$ wants to ask $Guan$ and $FWX$'s modem is broken, they have to go to $Guan$. Because there are so many "good people" in the township, the $FWX$ has to pay the tolls. $FWX$ wants to know how many tolls it needs to pay.(The town map is shown in the figure below)

Taking the town as a real matrix Amn, aij represents the toll to be paid here to ensure satisfaction. Please ask the minimum amount of tolls for $FWX$.(Note:$FWX$ can only move up, down, left and right)

Input Format:

The first row, two positive integers n, m, represent the size of the matrix.

The next n rows, m positive integers, represent the toll $FWX$ needs to pay at each node.(Note: The point where $FWX$ and $Guan$ are located is 0)

Output Format:

One line, a positive integer, represents the minimum toll required for $FWX$.

Input / output sample:

Enter # 1:

3 3
0 7 2
5 4 7
6 8 0

output #1:

16