Find Last Cell

Starting from the top-left corner, traverse the matrix one cell at a time in a counterclockwise spiral going down, right, up, then left. You land on the starting cell, and after that you skip one path cell before each landing; the count continues through turns, and the parity is never reset. Output the value of the last cell you land on.

输入格式

The input is N M followed by N lines of M integers each. The original wording of N/M as rows and columns contains a typo; this site specifies N rows and M columns. The original had no numeric bounds; this site adds 1≤N,M≤1000 and elements in −10^9..10^9.

输出格式

Output a single integer, the answer.

样例 1

输入：

3 3
29 8 37
15 41 3
1 10 14

输出：

41

样例 2

输入：

2 2
1 2
3 4

输出：

4

样例 3

输入：

1 4
9 8 7 6

输出：

7

样例说明

The outputs of the three public examples are, in order: 41; 4; 7. Verified by independent enumeration or direct simulation.