1
#include<cstdio>
2#include<cstring>
3#include<iostream>
4using namespace std;
5
6
const int dir[2][4]=
{{-1,-1,0,0},{-1,0,-1,0}};
7int F[120][60][60],a[60][60];
8int n,m;
9int Max(int x,int y)
10{
11
if (x>y) return x;
12 else return y;
13
}
14int Min(int x,int y)
15{
16 if (x>y) return y;
17 else return x;
18}
19int main()
20{
21 scanf("%d%d",&n,&m);
22 for (int i=1;i<=n;i++)
23 for (int j=1;j<=m;j++)
24 scanf("%d",&a[i][j]);
25 memset(F,0,sizeof(F));
26 int x;
27 for (int k=2;k<=n+m;k++)
28 for (int i1=1;i1<=Min(n,k-1);i1++)
29 for (int i2=1;i2<=Min(n,k-1);i2++)
30
{
31 x=a[i1][k-i1]+a[i2][k-i2];
32 if (i1==i2) x=a[i1][k-i1];
33 for (int i=0;i<=3;i++)
34 F[k][i1][i2]=Max(F[k][i1][i2],F[k-1][i1+dir[0][i]][i2+dir[1][i]]);
35 F[k][i1][i2]+=x;
36
}
37 printf("%d\n",F[n+m][n][n]);
38 return 0;
39}
40