import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		int[][] map = new int[n][m];
		for (int a = 0; a < n; a++) {
			for (int b = 0; b < m; b++) {
				map[a][b] = sc.nextInt();
			}
		}
		int[][] answer = new int[n][m];
		for (int a = 0; a < n; a++) {
			for (int b = 0; b < m; b++) {
				int count = 1;
				answer[a][b] = Math.max(dfs(a, b, count, n, m, map, 0), t(a, b, n, m, map));
			}
		}
		int finalanswer = 0;
		for (int a = 0; a < n; a++) {
			for (int b = 0; b < m; b++) {
				finalanswer = Math.max(finalanswer, answer[a][b]);
			}
		}
		System.out.println(finalanswer);
		sc.close();
	}

	private static int t(int a, int b, int n, int m, int[][] map) {
		int candidate1 = 0;
		int candidate2 = 0;
		int candidate3 = 0;
		int candidate4 = 0;
		if (b - 1 >= 0 && b + 1 < m && a + 1 < n) {
			candidate1 = map[a][b - 1] + map[a][b] + map[a][b + 1] + map[a + 1][b];
		}
		if (b - 1 >= 0 && b + 1 < m && a - 1 >= 0) {
			candidate2 = map[a][b - 1] + map[a][b] + map[a][b + 1] + map[a - 1][b];
		}
		if (b - 1 >= 0 && a - 1 >= 0 && a + 1 < n) {
			candidate3 = map[a][b - 1] + map[a][b] + map[a - 1][b] + map[a + 1][b];
		}
		if (a - 1 >= 0 && b + 1 < m && a + 1 < n) {
			candidate4 = map[a][b + 1] + map[a][b] + map[a - 1][b] + map[a + 1][b];
		}
		return Math.max(Math.max(candidate1, candidate2), Math.max(candidate3, candidate4));
	}

	private static int dfs(int a, int b, int count, int n, int m, int[][] map, int direction) {
		if (count == 4) {
			return map[a][b];
		} else {
			int candidate1 = map[a][b];
			int candidate2 = map[a][b];
			int candidate3 = map[a][b];
			int candidate4 = map[a][b];
			if (b + 1 < m && direction != 1) {
				candidate1 += dfs(a, b + 1, count + 1, n, m, map, 3);
			} else {
				candidate1 = 0;
			}
			if (a + 1 < n && direction != 2) {
				candidate2 += dfs(a + 1, b, count + 1, n, m, map, 4);
			} else {
				candidate2 = 0;
			}
			if (b - 1 >= 0 && direction != 3) {
				candidate3 += dfs(a, b - 1, count + 1, n, m, map, 1);
			} else {
				candidate3 = 0;
			}
			if (a - 1 >= 0 && direction != 4) {
				candidate4 += dfs(a - 1, b, count + 1, n, m, map, 2);
			} else {
				candidate4 = 0;
			}
			return Math.max(Math.max(candidate1, candidate2), Math.max(candidate3, candidate4));
		}
	}
}