#include <iostream>
#include <math.h>
#include <string>
#include <set>
#include <map>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
	long n, m;
	cin >> n >> m;
	vector<vector<long> > a(n + 1, vector<long> (m + 1, 0));
	for(long i = 1; i <= n; i++) {
		for(long j = 1; j <= m; j++) {
			cin >> a[i][j];
		}
	}
	for(long i = 1; i <= n; i++) {
		for(long j = 1; j <= m; j++) {
			a[i][j] += max(a[i][j - 1], max(a[i - 1][j - 1], a[i - 1][j]));
		}
	}
	cout << a[n][m];
	return 0;
}