#include<bits/stdc++.h>
using namespace std;
const int N=510;
int a[N][N],f[N][N];
int main()
{
	int r,c;
	cin>>r>>c;
	memset(f,-0x3f,sizeof f);
	for(int i=1;i<=r;i++)
		for(int j=1;j<=c;j++)
			cin>>a[i][j];
	f[0][1]=0;
	for(int i=1;i<=r;i++)
		for(int j=1;j<=c;j++)
			f[i][j]=max(f[i-1][j],f[i][j-1])+a[i][j];
	cout<<f[r][c]<<endl;
	return 0;
}