#include<cstdio>
#include<iostream>
using namespace std;
#define N 1000
#define MAX(a,b) (a)>(b)?(a):(b)
int a[N][N];
int dp[N][N];
int main()
{
	int n,m;
	while(scanf("%d%d",&n,&m)!=EOF)
	{
		for(int i = 1;i<=n;i++)
			for(int j = 1;j<=m;j++)
				scanf("%d",&a[i][j]);

		for(int i = 1;i<=n;i++)
			for(int j = 0;j<=m;j++)
				dp[i][j] = -1<<29;

		for(int j = 0;j<=m;j++)//初始化最外层为0
			dp[0][j] = 0;

		for(int i = 1;i<=n;i++)
			for(int j = i;j<=m;j++)
					dp[i][j] = MAX(dp[i][j-1],MAX(dp[i][j],dp[i-1][j-1] + a[i][j]));//跟前面与上面的最优值比较

		printf("%d\n",dp[n][m]);//最后的那个肯定是所有的值中最大的
	}
}