import java.util.Scanner;
public class Main {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
int N = sc.nextInt();
int M = sc.nextInt();
int[][] arr = new int[N + 1][M + 1];
for (int i = 1; i <= N; i++)
for (int j = 1; j <= M; j++)
arr[i][j] = sc.nextInt();
for (int i = 1; i <= N; i++)
for (int j = 1; j <= M; j++) {
int a = arr[i][j] + arr[i][j - 1];
int b = arr[i][j] + arr[i - 1][j];
arr[i][j] = a > b ? a : b;
}
System.out.println(arr[N][M]);
}
}