BAEKJOON 11048

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
	static int N, M;
	static int[][] dp;
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		N = Integer.parseInt(st.nextToken());
		M = Integer.parseInt(st.nextToken());
		dp = new int[N+1][M+1];
		for (int i = 1; i <=N; i++) {
			st = new StringTokenizer(br.readLine());
			for (int j = 1; j <=M; j++) {
				int n = Integer.parseInt(st.nextToken());
				dp[i][j] = Math.max(dp[i-1][j-1]+n, Math.max(dp[i-1][j] + n, dp[i][j-1] + n));
			}
		}
		System.out.println(dp[N][M]);
	}
}