1 #include <cstdio>
 2 #include <cmath>
 3 #include <iostream>
 4 using namespace std;
 5 
 6 int n,m,s;
 7 int dpx[222222],dpy[222222];
 8 
 9 int main ()
10 {
11     int i,j,k;
12     while (scanf ("%d%d",&n,&m)==2)
13     {
14         memset(dpx, 0, sizeof(dpx));
15         memset(dpy, 0, sizeof(dpy));//先对两个数组清零
16         for (i=2; i<=n+1; i++)
17         {
18             for (j=2; j<=m+1; j++)
19             {
20                 scanf ("%d",&s);
21                 dpx[j] = max(dpx[j-1], dpx[j-2] + s);//每个状态的值等于之前的某个状态加上另一个状态
22             }
23             dpy[i] = max(dpy[i-1], dpy[i-2] + dpx[m+1]);//因为只有加法，dpx[m+1]为每一行的最大值
24         }
25         printf ("%d\n",dpy[n+1]);
26     }
27     return 0;
28 }