BAEKJOON 14500

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

public class Main {
	static int ans, N, M;
	static int[][] map;
	static boolean[][] visit;
	static int dy[] = { -1, 1, 0, 0 }, dx[] = { 0, 0, -1, 1 };
	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());
		map = new int[N][M];
		visit = new boolean[N][M];
		for (int i = 0; i < N; i++) {
			st = new StringTokenizer(br.readLine());
			for (int j = 0; j < M; j++) {
				map[i][j] = Integer.parseInt(st.nextToken());
			}
		}
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < M; j++) {
				visit[i][j] = true;
				dfs(i, j, 0, 0);
				visit[i][j] = false;
				getSpecialSum(i, j);
			}
		}
		System.out.println(ans);
	}

	public static void dfs(int y, int x, int length, int sum) {
		if (length == 4) { 
			ans = Math.max(ans, sum);
			return;
		}
		for (int i = 0; i < 4; i++) {
			int ny = y + dy[i];
			int nx = x + dx[i];
			if (nx < 0 || ny < 0 || nx >= M || ny >= N||visit[ny][nx]) continue;
			visit[ny][nx] = true;
			dfs(ny, nx, length + 1, sum + map[ny][nx]);
			visit[ny][nx] = false;
		}
	}

	public static void getSpecialSum(int y, int x) {
		if (x - 1 >= 0 && y - 1 >= 0 && x + 1 < M) {
			int first = map[y][x] + map[y][x - 1] + map[y][x + 1] + map[y - 1][x];
			ans = Math.max(ans, first);
		}

		if (x - 1 >= 0 && y + 1 < N && x + 1 < M) {
			int second = map[y][x] + map[y][x - 1] + map[y][x + 1] + map[y + 1][x];
			ans = Math.max(second, ans);
		}

		if (x + 1 < M && y + 1 < N && y - 1 >= 0) {
			int third = map[y][x + 1] + map[y - 1][x] + map[y + 1][x] + map[y][x];
			ans = Math.max(third, ans);
		}

		if (x - 1 >= 0 && y - 1 >= 0 && y + 1 < N) {
			int forth = map[y][x - 1] + map[y - 1][x] + map[y + 1][x] + map[y][x];
			ans = Math.max(forth, ans);
		}
	}
}