//花束摆放问题，类似于背包，方程为f[i][j]=max{f[i][j-1],f[i-1][j-1]+a[i][j]} i=1..F, j=i+1..V
//初始f[i][i]预先算出来, f[0][]={0}, 结果为f[F][V]
//F为花朵数，V为花瓶数
#include <stdio.h>
#include <string.h>
const int S=105;
int a[S][S],f[S][S];
int main(){
int F,V,i,j;
scanf("%d%d",&F,&V);
for (i=1;i<=F;i++)
for (j=1;j<=V;j++)
scanf("%d",&a[i][j]);
memset(f,-63,sizeof(f));
memset(f[0],0,sizeof(f[0]));
for (i=1;i<=F;i++) f[i][i]=f[i-1][i-1]+a[i][i];
for (i=1;i<=F;i++)
for (j=i+1;j<=V;j++)
{
if (f[i][j]<f[i][j-1]) f[i][j]=f[i][j-1];
if (f[i][j]<f[i-1][j-1]+a[i][j]) f[i][j]=f[i-1][j-1]+a[i][j];
}
printf("%d\n",f[F][V]);
return 0;
}