Description

A square sheet of paper is partitioned into N*M equal squares by horizontal and vertical lines, 2 ≤ N ≤ 100, 2 ≤ M ≤ 100, N+M ≥ 7. A natural number not exceeding 20 000 is written in each square.

The task is to cut out a connected figure according to the following rules:

•  you can cut only along the drawn lines;
• the figure must contain exactly 6 squares;
• the figure must a cube evolvent, i.e. it must be possible to obtain a cube model by folding the figure along the drawn lines;
• the sum of the numbers on the evolvent must be the maximal possible.

Input

The first line contains two integers N and M separated by one or more spaces. The next N lines contain M integers each. The integers are separated by one or more spaces.

Output

This unique line contains the sum of the numbers on the found evolvent.

4 4
1 2 3 4
2 4 3 1
5 8 1 3
4 1 3 2

27

Source

Northeastern Europe 2003, Western Subregion